Salt-free diets are often prescribed to people with high blood pressure. The following data values were obtained from an experiment designed to estimate the reduction in diastolic blood pressure as a result of consuming a salt-free diet for 2 weeks. Assume diastolic readings to be normally distributed.
Before 109 105 109 107 106 91 106 105
After 104 98 100 99 105 86 103 95
(a) What is the point estimate for the mean reduction in the diastolic reading after 2 weeks on this diet? (Give your answer correct to one decimal place.)
(b) Find the 90% confidence interval for the mean reduction. (Give your answers correct to two decimal places.