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Consider the following table of the ages of our first six presidents


Ages of the first 6 presidents at inauguration


Washington 57

J. Adams 61

Jefferson 57

Madison 57

Monroe 58

JQ Adams 57


Find the mean of the data set

(57+61+57+57+58+57)/6 = 347/6 = 57.83


Find the standard deviation (showing all work)



How many of the presidentsÍ ages fall within one standard deviation of the mean?

Verified Answer :

\(m=57.83 \\ \sigma= \sqrt{ \frac{1}{N} \sum_{i=1}^{N}(x_i-m)^2 } = \\= \sqrt{ \frac{(57-57.83)^2+(61-57.83)^2+(57-57.83)^2+(57-57.83)^2+(58-57.83)^2+(57-57.83)^2}{6} } \\= \sqrt{ \frac{4(-0.83)^2+3.17^2+0.17^2}{6} } \approx 1.46 \\ \\x=57.83 \pm 1.46 \\57.83-1.46 \leq x \leq 57.83+1.46 \\56.35 \leq x \leq 59.29\)

Five presidents' ages fall within one standard deviation of the mean.

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