Ask an even number of your friends (but at least 10 of them) whether they own at least 2 credit cards. Randomly divide your response group (the population) into two samples of the same size (each of them containing half of your friends, no overlapps).
a) Compute the proportion of your friends who do own at least two credit cards for the whole population, and for both sample groups.
b) Are all three numbers the same? Explain.
c) Find the mean proportion for the two samples. Does it match the proportion for the whole population? Explain.