The Sudoku puzzle has recently becom e very popular all over the world. It is based on a 9 × 9 grid and the challenge is to fill in the grid so that every row, every column, and every 3 × 3 box contains the digits 1 through 9. A researcher is interested in estimating the average time taken by a college student to solve the puzzle. He takes a random sample of 8 college students and records their solving times as 1 4 , 7, 1 7 , 2 0 , 1 8 , 1 5 , 1 9 , 28 minutes.

a. Derive a 99% confidence interval of the average time taken by a college student to solve a Sudoku puzzle.

b. What assumption is necessary to make this inference? P-69