Answer the following questions FOR EACH study:
Study 1: A study was conducted using a sample of 200 customers of a large department store. As each customer left the store, they were asked their age and how long they had spent in the store. Their ages were classified into three groups, under 25 years, 25 to 40 years and over 40 years. The study found that younger customers generally spend less time in the store.
Study 2: Research suggests that people may be able to endure pain and discomfort better in the afternoon than in the morning. A dental researcher conducted a study by taking a random sample of 100 patients who had undergone similar treatment. Whether the patient received treatment in the morning or afternoon was recorded and then each patient was interviewed and a pain and discomfort tolerance score was assessed for them.
Study 3: Biologists suspect that the decline in the numbers of Silver Sword plants on the Hawaiian islands is due to goats eating them. A study is to be conducted in a national park in Hawaii to test this theory. To take into account that the goat population varies throughout the national park, the study is designed in the following way. 5 different sites at the national park are selected. 40 equal-sized plots of land are chosen, 8 at each site. For each site, 4 of the plots are randomly allocated to be left unfenced while the remaining 4 plots are fenced to keep goats out. The initial number of Silver Sword plants in each plot is counted. After a year, the number of Silver Sword plants in each plot is counted again and the percentage change in the number of plants is recorded
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 – you do this in (i).
(iii) Would you describe the study as an experiment or an observational study? Referring to the study design, justify your answer. (I.e., what part of the study design led you to this conclusion?)
(b) Which one of the studies used blocking? Also correctly describe what was blocked.
(c) Which one of the studies used a control group? Also correctly describe the control group.
(d) Which of the studies, if any, could be used to establish causation? To get the mark, you must also briefly justify your answer.
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