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A little extra background on standard deviations above and below the mean

If, for example, a set has a standard deviation of 4, then:
1 standard deviation = 4
2 standard deviations = 8
3 standard deviations = 12
1.5 standard deviations = 6
0.25 standard deviations = 1
etc


So, if the mean of a set is 9, and the standard deviation is 4, then:
2 standard deviations ABOVE the mean = 17 [since 9 + 2(4) = 17]
1.5 standard deviations BELOW the mean = 3 [since 9 - 1.5(4) = 3]
3 standard deviations ABOVE the mean = 21 [since 9 + 3(4) = 21]
etc.
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In a population of chickens, the average (arithmetic mean) weight is 6.3 pounds, and the standard deviation is 1.2 pounds. Which of the following weights (in pounds) are within 1.5 units of the standard deviation of the mean?

1.5 units of standard deviation ABOVE the mean = 6.3 + (1.5)(1.2) = 8.1
1.5 units of standard deviation BELOW the mean = 6.3 - (1.5)(1.2) = 4.5

So, the weights that are WITHIN 1.5 units of the standard deviation of the mean will be BETWEEN 4.5 and 8.1

Answer: B, C, D, E, F, G

Cheers,
Brent