2.2 Study design

A student group was studying this RQ (which is not appropriate for the SCI110 Project): 'Among Australians, is the average serum cholesterol concentration different for smokers and non-smokers?'

The students gave the following information about their study. Explain why each of these statements is incorrect.

"The design is observational, as we cannot manipulate each person's serum cholesterol."
"The Outcome is 'the average serum cholesterol concentration for smokers and non-smokers'."
"The study is not externally valid, as the results may not apply to all people in the world."
"The response variable is serum cholesterol."
"In this experiment, the population is 'Australians'."
"The data file will have two columns: one for smokers, and one for non-smokers."
"'Whether or not the person owns a cat' is likely to be a confounding variable."
"The observer effect is not relevant, as the participants will know they are involved in a study."