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JAMB 1997 · UME · Q47

Find the standard deviation of the data −5,−4,−3,−2,−1,0,1,2,3,4,5-5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5.

Worked solution (try it first)
  1. The numbers are symmetric about 0, so the mean is 0 and each deviation is the number itself.
  2. ∑x2=2(1+4+9+16+25)=110\sum x^2 = 2(1 + 4 + 9 + 16 + 25) = 110.
  3. There are 11 numbers, so the variance is 11011=10\frac{110}{11} = 10 and the standard deviation is 10\sqrt{10}, option C.

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