According to an early CDC study of 21 patients infected with the swin flu, the average incubation period was 7 days with a sample standard deviation of 4.5 days. We will assume that the incubation times are normall distributed. Find a 95% confidence interval for the true average incubation period. Use Minitab for your computations. Solution Given n=21, xbar=7, s=4.5 a=0.05, |t(0.025,df=n-1=20)|=2.09 (check student t table) So 95% CI is xbar ± t*s/n --> 7 ± 2.09*4.5/sqrt(21) --> ( 4.947661, 9.05234).

1. According to an early CDC study of 21 patients infected with the swin flu, the average
incubation period was 7 days with a sample standard deviation of 4.5 days. We will assume that
the incubation times are normall distributed.
Find a 95% confidence interval for the true average incubation period. Use Minitab for your
computations.
Solution
Given n=21, xbar=7, s=4.5
a=0.05, |t(0.025,df=n-1=20)|=2.09 (check student t table)
So 95% CI is
xbar ± t*s/n
--> 7 ± 2.09*4.5/sqrt(21)
--> ( 4.947661, 9.05234)