Sorry to bother you! When calculating the variance in the second question of this question, why is the denominator n-1? Is there a more intuitive way to understand this?

Chapter 12 on 9. Calculating Returns and Variability [LO1] You've observed the following returns Crash-n-Burn Computer's stock over the past five years: 8 percent, -15 percent, 19 percent, 31 percent, and 21 percent. a. What was the arithmetic average return on the company's stock over this five-year period? b. What was the variance of the company's returns over this period? The standard deviation