Explain whether you think the Rule for Sample Means applies to each of the following situations. If it does apply, specify the population of interest and the measurement of interest. If it does not apply, explain why not.
a. A researcher is interested in what the average cholesterol level would be if people restricted their fat intake to 30% of calories. He gets a group of patients who have had heart attacks to volunteer to participate, puts them on a restricted diet for a few months, and then measures their cholesterol.
b. A large corporation would like to know the average income of the spouses of its work­ers. Rather than go to the trouble to collect a random sample, they post someone at the exit of the building at 5 p.m. Everyone who leaves between 5 p.m. and 5: 30 p.m. is asked to complete a short questionnaire on the issue; there are 70 responses.