Question

The mean diastolic blood pressure for a random sample of 90 people was 85 millimeters of mercury. If the standard deviation of individual blood pressure readings is known to be 10 millimeters of mercury, find a 90% confidence interval for the true mean diastolic blood pressure of all people. Then complete the table below.

Carry your intermediate computations to at least three decimal places. Round your answers to one decimal place. (If necessary, consult a list of formulas.)

What is the lower limit of the 90% confidence interval? What is the upper limit of the 90% confidence interval?

Answer 1

We need to construct the 90% confidence interval for the population mean μ. The following information is provided:

Sample Mean $\bar{X}$ =	8585
Population Standard Deviation (σ) =	1010
Sample Size(N) =	9090

The critical value for α=0.1 is Z_c​ = Z_1−α/2​ = 1.645. The corresponding confidence interval is computed as shown below:

Jn Vn 10 .BIİ I.G4S 90' 10 1.64:: ''' = 185 8:i (83.266.86.734) =

The lower limit of the 90%confidence interval = 83.266

The upper limit of the 90%confidence interval = 86.734