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Find the variance of the 11 numbers 7, 11, 15, …, 47 (they go up in steps of 4).

Competition practiceStatistics

A176
B160
C40
D12.65

Step-by-Step Solution

For

n

equally spaced values with gap

d

, variance

= \frac{d ^{2} ( n ^{2} - 1 )}{12} = \frac{16 \times 120}{12} = 160

. (40 uses

d

instead of

d^{2}

; 12.65 is the SD.)

Answer: B) 160

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