study was developed to evaluate effectiveness of a weight loss diet plan. An ad was placed in two towns tolocate study participants who were to follow the diet. In Town A, the clinicians asked each dieter to report how much weight they had lost over the previous 6weeks while following the diet. In Town B, the clinicians weighed each dieterat the beginning of the study and again after 6 weeks on the diet program. The weight lost wascalculated as the difference between the beginning weight and the weight after 6 weeks. At the end of the study, it was determined that Town B had lostsignificantly less weight than Town A.

a) What is the population of interest in this situation?

b) What type(s) of sampling error or bias is(are) present in this example?