1. If x is a normally distributed variable with = 100 and = 5, find the lower and upper x values that will include 90% of the data.

Lower x value =

Upper x value =

1. In September a biological research team caught, weighed, and released a random sample of 24 chipmunks in Rocky Mountain National Park. The mean of the sample weights was x-bar = 8.7 oz. with sample standard deviation s = 1.4 oz. Find a 90% confidence interval for the mean September weight of all chipmunks in Rocky Mountain National Park.

1. A legislative aide is doing research on the duration of calls initiated on car cellular phones. A preliminary study showed that the standard deviation of these calls is 1.6 minutes. How large a sample will be needed for the aide to be able to state with 99% confidence that the sample mean duration time for the calls differs from the population mean by no more than 0.20 minutes?