Question

The mean diastolic blood pressure for a random sample of 90 people was 81 millimeters of mercury. If the standard deviation of individual blood pressure readings is known to be

11 millimeters of mercury, find a 95% confidence interval for the true mean diastolic blood pressure of all people. (upper and lower) Round to three decimal places.

Answer 1

Given that, population standard deviation = 11 millimetres

sample size (n) = 90 and sample mean = 81 millimetres

A 95% confidence level has significance level of 0.05 and critical value is,

The 95% confidence interval for the population mean is,

Therefore, the  95% confidence interval for the true mean diastolic blood pressure of all people is (78.727, 83.273) millimetres.

Where, lower bound = 78.727 millimetres and

upper bound = 83.273 millimetres