The ages (years) of the four U.S. presidents when they were assassinated in office are 56 (Lincoln), 49 (Garfield), 58 (McKinley), and 46 (Kennedy). Consider these four ages to be a population.
a. Assuming that two of the ages are randomly selected to form samples of size n = 2 with replacement, find the mean of each of the 16 possible samples.
b. What is the mean of the sample means from part a?
c. Is the mean of the sample means equal to the mean of the population of the four ages? Are those means always equal?