The pregnancy length in days for a population of new mothers can be approximated by a normal distribution with a mean of 265 days and a standard deviation of 12 days. What is the minimum pregnancy length that can be in the top 10% of pregnancy lengths?
We have given following information,
Mean = days
Standard deviation = days
Calculating the z-value corresponding to top 10% i.e. 90th percentiles i.e. p = 0.90
z(p=0.10) = 1.28155 (From excel =NORM.S.INV (0.90))
Z = =
X = (1.28155*12) + 265
X = 280.37
Minimum pregnancy length that can be in the top 10% of pregnancy lengths is 280.37 days.
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