Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity

Question an investigator wanted to test the effectivenss of a new drug designed to prevent people being infected with influenza. They selected 200 participants from the population and randomly assigned each person to one of two groups. The first group (control) was given a placebo (tablet with no active ingredient in it) while the second group (treatment) was given an identical looking tablet containing the new pharmaecutical. Tablets were administered to the control group on a weekly basis for the first six months and then to the treatment group for the next six months. After the trial periods, the participants who contracted influenza from each group were recorded and compared. a) what are the indepedent and dependent variables in this study? b) what type of design was used in the study. Give reason for your decision c) suggest some possible extraneous variables that may have arisen in study d) suggest a possible confounding factor evident in the study e) what changes would you make to this study to improve its internal validity