Question

The effectiveness of a blood-pressure drug is being investigated. An experimenter finds that, on average, the reduction in systolic blood pressure is 27.8 for a sample of size 26 and standard deviation 7.3. Estimate how much the drug will lower a typical patient's systolic blood pressure (using a 80% confidence level). Assume the data is from a normally distributed population. Enter your answer as a tri-linear inequality accurate to three decimal places.

Answer 1

Solution :

Degrees of freedom = df = n - 1 = 25

At 80% confidence level the t is ,

= 1 - 80% = 1 - 0.80 = 0.20

/ 2 = 0.20 / 2 = 0.10

t _/2,df = t_0.10,25 = 1.316

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

= 1.316 * ( 7.3/ 26)

= 1.884

The 80% confidence interval estimate of the population mean is,

- E < < + E

27.8 - 1.884 < < 27.8 + 1.884

25.916 < < 29.684