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?
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.