Confidence interval for the population mean: Use of the standard normal

Scenario: The meandiastolic blood pressure for a random sampleof 90 people was 92 millimeters of mercury. If the standard deviationof individual blood pressure readings is known to be 12 millimeters of mercury, find a 90% confidence intervalfor the true mean diastolic blood pressure of all people. Then complete the questions below:

Carry your intermediate computations to at least three decimal places. Round your answers to one decimal place.

a) What is the lower limit of 90% confidence interval?

b) What is the upper limit of 90% confidence interval?

m = 92, s = 12, n = 90

Standard Error of the mean, SE = s/sqrt n = 12/sqrt 90 = 1.2649

The …

This solution provides a complete and organized step by step method illustrating how to calculate the confidence interval for variance. Formulas for the calculations and an interpretation of the results are also included. Student’s will find that this solution is easy to follow.