Question

The ages of members of a stamp collecting group are normally distributed with a mean of 55 years and a standard deviation of 4 years.

There are 123 members in the group.

About how many members are expected to be between 51 years old and 59 years old?

Answer 1

82 members

Explanation:

51 is one standard deviation to the left of the mean.

59 is one standard deviation to the right of the mean

approximately 2/3 of the data normally distributed is within 1 standard deviation of the mean.

so we expect 2/3 of the data (2/3 X 123 = 82).

so the answer is 82 members