According to an avid aquarist, the average number of fish in a
20-gallon tank is 10, with a standard deviation of two. His friend,
also an aquarist, does not believe that the standard deviation is
two. She counts the number of fish in 15 other 20-gallon tanks.
Based on the results that follow, do you think that the standard
deviation is different from two? Data: 11; 10; 9; 10; 10; 11; 11;
10; 12; 9; 7; 9; 11; 10; 11...