Using subtraction of normal variables, it is found that Riley is not correct, as the mean is of 8 - 8 = 0.
The mean is the subtraction of the means, while the standard deviation is the square root of the sum of the variances.
Researching this problem on the internet, it is found that, for both samples, the mean is of 8, hence:
8 - 8 = 0.
Thus, Riley is not correct.
More can be learned about the subtraction of normal variables at https://brainly.com/question/14397951