Question

Sudoku is a puzzle consisting of squares arranged in 9 rows and 9 columns. The 81 squares are further divided into nine 3 ✕ 3 square boxes. The object is to fill in the squares with numerals 1 through 9 so that each column, row, and box contains all nine numbers. However, there is a requirement that each number appear only once in any row, column, or box. Each puzzle already has numbers in some of the squares.

Alisha wants to do a statistical study to determine how long it takes people to complete a Sudoku puzzle. Her plan is as follows.

Download 10 different puzzles from the Internet.
Find 10 friends willing to participate.
Ask each friend to complete one of the puzzles and time him- or herself.
Gather the completion times from each friend.

Describe some of the problems with Alisha's plan for the study. (Note: Puzzles differ in difficulty, ranging from beginner to very difficult. SELECT ALL THAT APPLY.)

A. There are actually only 9 different Sudoku puzzles.

B. Some Sudoku puzzles don't have solutions.

C. It is not clear that all puzzles have the same difficulty.

D. Self-timing may lead to some inaccurate measurements.

E. Friends having different levels of experience.

Are the results from Alisha's study anecdotal, or do they apply to the general population?

A. The results will be anecdotal, due to issues with the plan for the study.

B. The results will only apply to Alisha's circle of friends so we cannot extend them to the general population.    

C. The results will apply to the general population.

Answer 1

Problems with Alisha's plan for the study are:

A) is not correct as there aren't only 9 different sudoku puzzles.
B) is not correct as well. All valid puzzles have a solution
C) is not correct as puzzles have a difficulty level which is stated ranging from beginner to very difficult.
D) is correct as self timing may lead to inaccurate measurements.
E) is correct as everyone has different levels of experience with solving the puzzles.

Hence, only D) and E) are correct.

The results cannot apply to the general population as her friends are not representative of everyone. The results will be anecdotal due to some problems with the study. A) is correct.