Question

The effectiveness of a blood-pressure drug is being investigated. An experimenter finds that, on average, the reduction in systolic blood pressure is 72.5 for a sample of size 27 and standard deviation 7.3. Estimate how much the drug will lower a typical patient's systolic blood pressure (using a 95% confidence level). Assume the data is from a normally distributed population.

Enter your answer as a tri-linear inequality accurate to three decimal places.

< μμ <

Answer 1

Solution :

Given that,

= 72.5

s = 7.3

n = 27

Degrees of freedom = df = n - 1 = 27 - 1 = 26

At 95% confidence level the t is ,

  = 1 - 95% = 1 - 0.95 = 0.05

/ 2 = 0.05 / 2 = 0.025

t _/2,df = t_0.025,26 =2.060

Margin of error = E = t_/2,df * (s /n)

= 2.060 * (7.3 / 27 )

= 2.888

Margin of error = 2.888

The 99% confidence interval estimate of the population mean is,

- E < < + E

72.5 - 2.888 < < 72.5 +2.888

69.612 < < 75.388

(69.612, 75.388 )