Question

1. A random sample of 11 men’s pulse rates showed a mean of 71.7 beats per minute and a standard deviation of 15.7. Assume that pulse rates are normally distributed. Use the table to find a 90% confidence interval for the population mean pulse rate of mean.

Answer 1

Solution :

Given that,

= 71.7

s =15.7

n = 11

Degrees of freedom = df = n - 1 = 11 - 1 = 10

At 90% confidence level the t is ,

= 1 - 90% = 1 - 0.90 = 0.1

/ 2 = 0.1 / 2 = 0.05

t _/2,df = t_0.05,10 =1.813

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

= 1.813 * (15.7 / 11) = 8.58

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

- E < < + E

71.7 - 8.58 < < 71.7 + 8.58

63.12 < < 80.28

(63.12 , 80.28)