The heights in cm, of 10 children are 145, 163, 159, 162, 167, 149, 150, 160, 170, and 155. The standard deviation of the heights of the children is
A. 5.5cm
B. 5.7cm
C. 6.5cm
D. 6.7cm
E. 7.7cm
Correct Answer: E
Explanation
Let's calculate the standard deviation.
1. Calculate the Mean:
The mean height is:
\[
\text{Mean} = \frac{145 + 163 + 159 + 162 + 167 + 149 + 150 + 160 + 170 + 155}{10} = \frac{1,580}{10} = 158
\]
2. Calculate Each Squared Difference from the Mean:
\[
(145 - 158)^2 = (-13)^2 = 169
\]
\[
(163 - 158)^2 = 5^2 = 25
\]
\[
(159 - 158)^2 = 1^2 = 1
\]
\[
(162 - 158)^2 = 4^2 = 16
\]
\[
(167 - 158)^2 = 9^2 = 81
\]
\[
(149 - 158)^2 = (-9)^2 = 81
\]
\[
(150 - 158)^2 = (-8)^2 = 64
\]
\[
(160 - 158)^2 = 2^2 = 4
\]
\[
(170 - 158)^2 = 12^2 = 144
\]
\[
(155 - 158)^2 = (-3)^2 = 9
\]
Sum of squared differences:
\[
169 + 25 + 1 + 16 + 81 + 81 + 64 + 4 + 144 + 9 = 594
\]
Calculate the Variance:
\[
\text{Variance} = \frac{504}{10} = 59.4
\]
Calculate the Standard Deviation:
\[
\text{Standard Deviation} = \sqrt{59.4} \approx 7.7
\]
The corrected standard deviation of the heights is approximately 7.7cm.