One forth of one third of two fifths of a number is 15. What is the number?
2 answers:
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A suitable probability calculator will show that probability to be .135905122.
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Your class extends from 1 standard deviation above the mean to 2 standard deviations above the mean. The empirical rule puts that probability at ...
... (1/2)(95% - 68%) ≈ 13.5%
The empirical rule tells you 68% of observations lie within 1 standard deviation of the mean, and 95% lie within 2 standard deviations. Then the number that lie between 1 and 2 standard deviations from the mean will be the difference of these values. You want the values in the region above the mean only, so you only want half the difference just described.
