Consider the following studies: An education researcher wants to know if volunta
ID: 3269331 • Letter: C
Question
Consider the following studies: An education researcher wants to know if voluntary participation in organised sports differs between state schools and private schools. 20 state high schools and 20 private high schools are selected at random from lists of New Zealand schools. The schools are contacted and asked to collect information on the percentage of their students who voluntarily participate in organised sports. The manager of an advertising company was interested in whether longer television ads were more or less effective than shorter ads. 160 people were recruited for the study. The people were randomly divided into two groups. Both groups were shown 60 minutes of television which included a 45-minute programme with three 5-minute breaks for ads. For the first group the ads included a 30-second ad for a new type of cell phone played in each of the three breaks while the second group had a 60-second ad for the same cell phone in each of the three breaks. Afterwards, all participants were interviewed and asked a series of questions about the cell phone and a recall score was computed for them. (a) Answer the following questions FOR EACH study: (i) Identify the groups that are being compared. (I.e., what treatments or factors of interest are being compared?) DO NOT also say what is being measured to make the comparison - you do this in (ii). (ii) What is being measured to compare these groups? ONLY describe the variable being measured. DO NOT also mention the groups being compared. (iii) Would you describe the study as an experiment or an observational study? - If it was an experiment, what part of the study design led you to this conclusion? - If it was an observational study, could an experiment have been easily carried out instead? If so, briefly explain how. If not, briefly explain why not (b) Could the results of a study such as study 2 be used to argue that any overall difference in the recall scores is due to the length of the ad? Briefly justify your answer. (c) Can blinding be used at all in Study 2? If so, describe how. (d) It was later suggested that age could be a significant factor in Study 2. How could the study design be modified to take into account the age effect?Explanation / Answer
(a)
(i) Study 1: State High School, Private High School
Study 2: Longer TV ads, Shorter TV Ads
(ii)
Study 1: Percentage of Students who voluntary participate in organised sports
Study 2: Recall score to measure effectiveness of Ads
(iii)
Both studies are experiment as both methods apply treatments to a group and recording the effects.
Study 1: It is an observational study where researchers simply collect data based on what is seen and heard and infer based on the data collected.
It could not be carried out as an experiment, as treatments here are being student of State High School, Private High School. And the random group of people cannot be just admitted to these schools to performed the experiment.
Study 2: It is experiment as the methods apply treatments to a group and recording the effects.
The people were randomly divided into two groups and given treatments to watch 30 and 60 second Ads.
(b)
The age and gender of the people can act as the confounding variable in the experiment.
But as the people were randomly divided into two groups and ads for same product was shown (only the length was different), the effect of confounding variable may be minimum.
So, the difference in the recall scores may only be due to length of ads.