D.7 Answers: Designing experimental studies

Answers to exercises in Sect. 7.8.

Answer to Exercise 7.2: The observer effect. The researcher is directly contacting the subjects, so may unintentionally influence their responses.

Answer to Exercise 7.3: 1. Randomly allocate the type of water to the subject (or the order in which the subjects taste-test each drink.) 2. The subjects do not know which type of water they are drinking. 3. The person providing the water and receiving the ratings does not know which type of water they are drinking. 4. Hard to find a control. 5. Any random sampling is good, if possible.

Answer to Exercise 7.4: 1. Response: The amount of sunscreen used; Explanatory: The time spent on sunscreen application. 2. They were looking at potential confounding variables. 3. If the mean of both the response and explanatory variables was different for females and males, then the sex of the participant would be a confounding variable, and this would need to be factored into the analysis of the data. 4. The participants are blinded to what is happening in the study.