Answer:
Approximately 68% of their scores will fall within one standard deviation of the mean.
Step-by-step explanation:
The Empirical Rule states that, for a normally distributed random variable:
68% of the measures are within 1 standard deviation of the mean.
95% of the measures are within 2 standard deviation of the mean.
99.7% of the measures are within 3 standard deviations of the mean.
In this problem, we have that:
By the Empirical Rule, approximately 68% of their scores will fall within one standard deviation of the mean.