Marla G. answered 10/24/21
Effective Math Tutor Specializing in Statistics and Study Skills.
What does part a) wants you to do?
For part b). I don't know of any "short-cut" to do this problem. To calculate the sample mean: I think you will need to literally list all the possible subsets of size=3. Then go back & calculate the mean for each subset. Then, go back and calculate the mean of all those means (mean of each subset). This is often called the 'standard error of the mean', and tells you how well you are estimating the mean of the population of interest.
To calculate the population mean, simply find the mean of the 5 values given as the 'population'.
For part c) just follow the directions given, and use the range (highest & lowest) to estimate the dispersion in the population and the list of sample means for each subset.
FYI: I expect the population dispersion to be greater than that of the sample means, it usually is.