Answer:
Two standard deviations
Explanation:
The Z score is obtained using the mean and standard deviation, according to the empirical. Rule, which gives percentage of values that lie within an interval estimate in a normal distribution ;
one standard deviation lie within 68% of the mean
Two standard deviations lie within 95%
Three standard deviations lie within 99.7%
Hence, for the question given, 95% fall within 2 standard deviations of the mean