Question

The effectiveness of a blood-pressure drug is being investigated. An experimenter finds that, on average, the reduction in systolic blood pressure is 64.2 for a sample of size 1008 and standard deviation 19.9.

Estimate how much the drug will lower a typical patient's systolic blood pressure (using a 90% confidence level).

Enter your answer as a tri-linear inequality accurate to one decimal place (because the sample statistics are reported accurate to one decimal place).

< μ μ <

Answer 1

Confidence interval for Population mean is given as below:

Confidence interval = Xbar ± t*S/sqrt(n)

From given data, we have

Xbar = 64.2

S = 19.9

n = 1008

df = n – 1 = 1007

Confidence level = 90%

Critical t value = 1.6464

(by using t-table)

Confidence interval = Xbar ± t*S/sqrt(n)

Confidence interval = 64.2 ± 1.6464*19.9/sqrt(1008)

Confidence interval = 64.2 ± 1.0319

Lower limit = 64.2 - 1.0319 =63.17

Upper limit = 64.2 + 1.0319 = 65.23

Confidence interval = (63.17, 65.23)

63.17 < µ < 65.23