Scientists measured the lengths of a species of lizard in a region. The graph below shows that the measured lengths have a normal distribution.

Question

The graph shows the normal distribution of length in centimeter from 10 to 34 along the horizontal line has a symmetrical bell-shaped curve and the highest frequency is represented by a dashed line at 22, the tail of the curve stretches to the left and runs along the horizontal axis beyond 10 towards infinity, and the tail of the curve stretches to the right and runs along the horizontal axis beyond 34 towards infinity. There are 2 vertical grey lines to the curve each to the left at 18 and 14 and to the right at 26 and 30.

A lizard that is one standard deviation below the mean is ______ long.
A.
10 cm

B.
14 cm

C.
18 cm

D.
20 cm

Answer 1

In a normal distribution, the mean (average) is the highest point of the distribution curve. The graph you described indicates that the mean length of the lizard population is 22 cm, as represented by the dashed line.

A standard deviation below the mean would be calculated by subtracting one standard deviation from the mean. According to the information provided, it appears that one standard deviation below the mean would correspond to the vertical line at 18 cm. Therefore, a lizard that is one standard deviation below the mean would be:

C. 18 cm