A physics class had two exams. On the first exam the mean score was $70$ with a

standard deviation of $10.$ On the second exam the mean score was $60$ with a

standard deviation of $15.$ The correlation coefficient between the scores of the

two exams was $r=0\mathrm{.}6.$ We run a regression analysis with the first exam score as

the independent variable and the second exam score as the dependent variable.

We use the result to estimate the score on the second exam for each student

based on their score on the first exam. For at least $75\%$ of the students in the

class, the regression estimated score for the second exam will be correct to

within how many points? hint : the answer is not $64\mathrm{.}5$ or$65$