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JAMB Mathematics 2020 Paper

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Question : 21

Total: 40

Calculate the standard deviation of the following data: 7, 8, 9, 10, 11, 12, 13

2
4
12
17

Solution:

Concept:

Standard deviation measures how spread out the data values are from the mean.

Explanation:

Mean,

\bar{x} = \frac{7 + 8 + 9 + 10 + 11 + 12 + 13}{7} = \frac{70}{7} = 10

.

Deviations from the mean:

-3, -2, -1, 0, 1, 2, 3

.

Squared deviations:

9, 4, 1, 0, 1, 4, 9

.

Sum of squared deviations:

9 + 4 + 1 + 0 + 1 + 4 + 9 = 28

.

Variance:

\frac{28}{7} = 4

.

Standard deviation:

\sqrt{4} = 2

.

Answer:

Standard deviation

= 2

, so the correct option is A. 2.

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