Sports and Leisure In 1974, Erno Rubik created an imaginative and best-selling puzzle—the Rubik’s cube. Many countries hold competitions in which participants try to solve this puzzle as quickly as...

Sports and Leisure In 1974, Erno Rubik created an imaginative and best-selling puzzle—the Rubik’s cube. Many countries hold competitions in which participants try to solve this puzzle as quickly as possible. The text website provides a sample from the list of record times (in seconds) in official world competitions.²⁹

a. Find the actual proportion of observations within one standard deviation of the mean, within two standard deviations of the mean, and within three standard deviations of the mean.

b. Using the results in part (a), do you think the shape of the distribution of national record times is normal? Why or why not?

c. Construct a histogram for these data. Describe the shape of the distribution.