Question

A sample of 75 concrete blocks had a mean mass of 38.3 kg with a standard deviation of 0.4 kg.

Find a 95% confidence interval for the mean mass of this type of concrete block. (Round the final answers to three decimal places.)

The 95% confidence interval is

Answer 1

Solution :

degrees of freedom = n - 1 = 75 - 1 = 74

t/2,df = 1.993

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

= 1.993 * ( 0.4 / 75)

Margin of error = E = 0.092

The 95% confidence interval estimate of the population mean is,

  ± E

38.3 ± 0.092

(38.208 , 38.392)