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Practice Problem:
Probability and Normal Distribution
- Problem
- For the normal distribution N(50,20) --- that is
that has a mean of 50 and a standard deviation of
20 --- find X such that 71.57% of the area under the
curve is to the left of X.
- Answer
- The Z-Score is .57 because it has .7157 of the
area to the left of it.
This means that X is .57 population standard
deviation units above the population mean.
- Therefore:
X = PopMean + .57 PopStDv
X = 50 + .57*20
X = 50 + 11.4
X = 61.4
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