Question

The effectiveness of a blood-pressure drug is being investigated. An experimenter finds that, on average, the reduction in systolic blood pressure is 20.7 for a sample of size 464 and sample standard deviation 21.4.

Estimate how much the drug will lower a typical patient's systolic blood pressure (using a 99% 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).

< μμ <

Answer should be obtained without any preliminary rounding.

d) Interpret the confidence interval in the words of the problem.

Answer 1

Given that,

= 20.7

s =21.4

n =464

Degrees of freedom = df = n - 1 =464 - 1 = 463

At 90% confidence level the t is ,

= 1 - 90% = 1 - 0.90 = 0.1

/ 2 = 0.1 / 2 = 0.05

t /2,df = t0.05,463 = 1.648    ( using student t table)

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

= 1.648 * (21.4 / 464) = 1.6

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

- E < < + E

20.7 - 1.6 < <20.7 + 1.6

19.1< < 22.3

( )