Let x be the mean (in points) and s be the standard deviation (in points) of three test scores, x1, x2, and x3, all in points.
a. Write a formula for the mean of the three test scores.
b. Use the formula you found in part (a) to show that if all three test scores are equal, then the mean score is x1.
c. Write a formula for the standard deviation of the three test scores.
d. Use the formula you found in part (c) to show that if all three test scores are equal, then the standard deviation of the three test scores is 0 points.