A researcher collected sample data for 20 middle-aged women. The sample had a mean serum cholesterol level (measured in milligrams per one hundred milliliters) of 189.4 with a standard deviation of

9.6. Assuming that serum cholesterol levels for middle-aged women are normally distributed, find a

95% confidence interval for the mean serum cholesterol level of all women in this age group. Give the lower limit and upper limit of the 95% confidence interval.

Carry your intermediate computations to at least three decimal places.