Question 579009: Suppose SPS professors have an average life normally distributed of 82 years, with a population standard deviation of 5 years.
a) What percent of SPS professors will make it past the age of 70?
b) What percent of SPS professors will not live more than 80 years?
c) Calculate the 95th percentile.
d) What proportion of SPS professors will live between 85 and 90 years?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Suppose SPS professors have an average life normally distributed of 82 years, with a population standard deviation of 5 years.
a) What percent of SPS professors will make it past the age of 70?
z(70) = (70-82)/5 = -12/5
P(x > 70) = P(z > -12/5) = 0.9918
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b) What percent of SPS professors will not live more than 80 years?
z(80) = (80-82)/5 = -2/5
P(x <= 80) = P(z <= -2/5) = 0.3446
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c) Calculate the 95th percentile.
InvNorm(0.95) = 1.645
x = 1.645*5+82 = 90.225
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d) What proportion of SPS professors will live between 85 and 90 years?
Using a TI-84: P(85<= x <=90) = normalcdf(85,90,82,5) = 0.2195
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Cheers,
Stan H.
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