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The length of a human pregnancy is normally distributed with a mean of 272 days with a standard deviation
of 9 days (Bhat & Kushtagi, 2006). How many days would a pregnancy last for the shortest 20%? Round answer to 2 decimal places.
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You are given a normal curve with the mean value of 272 days and the standard deviation of 9 days.
They want you find a raw mark t (days) such that 20%, or 0.2 of the area under the normal curve
be on the left of the mark t.
Use a standard function invNorm in your calculator TI-83/84
area mean SD <<<---=== formatting pattern
t = invNorm(0.2, 272, 9)
and get the ANSWER t = 264.43 days.
Solved.