question in statics and probability

Question

According to an avid aquarist, the average number of fish in a 20-gallon tank is ten, 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

Answer 1

You can put the data into a spread sheet to do relevant calculations. Here is an example: https://docs.google.com/spreadsheets/d/1QRxh3VGGXAtiJMSjn0xQOXx3sX_BoBszKDLAkyJEi24/edit?usp=sharing

Have a look and see if you can understand the formulas.

20.933/15 = 1.396

1.181