Forty subjects were assigned to a particular weight loss diet. By the end of a year, 20 of the subjects had dropped out of the study The mean weight loss for those who remained was 2.1 kilograms.
a. Is 2.1 kilograms an unbiased estimate for the mean weight loss by all subjects who would be assigned that diet?
b. What would the mean weight loss for the original 40 subjects be if the 20 who dropped out actually gained an average of 2.1 kilograms?