The distribution of the time it takes for different people to solve a certain crossword puzzle is strongly skewed to the right, with a mean of 30 minutes and a standard deviation of 15 minutes. the distribution of z-scores for those times is

z-scores illustrates how far a data element is, from the mean of the dataset.

Given

--- the mean

--- the standard deviation

z-score is calculated using:

(a) The z-score of the mean

This means that:

So, we have:

(b) The z-score of the standard deviation

This means that:

So, we have:

Hence, the distributions of z-score for the mean and the standard deviation are 0 and -1 respectively.

Read more about z-scores at:

link