Students in a large district's two high schools are offered a "Second Breakfast' program after their first-period class. The district's nutrition manager is interested in determining if the program is effective. He takes two independent
random samples of days from the previous years, 20 from high school A and 15 from high school B, and calculates
the mean amount of money, in dollars spent for the program. Which of the following statements concerning the
variability of the sampling distribution of the sample mean is correct?