Question

The effectiveness of a blood-pressure drug is being investigated. An experimenter finds that, on average, the reduction in systolic blood pressure is 65.3 for a sample of size 415 and standard deviation 11.7. 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 < ____

Answer 1

Solution :

degrees of freedom = n - 1 = 415 - 1 = 414

t/2,df = 1.658

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

= 1.658 * ( 11.7 / 415)

Margin of error = E = 1.0

The 90% confidence interval estimate of the population mean is,

- E < < + E

65.3 - 1.0 < < 65.3 + 1.0

64.3 < < 66.3