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 99% confidence interval for the mean mass of this type of concrete block. (Round the final answers to three decimal places.)

The 99% confidence interval is

Answer 1

Given,

X_bar = 38.3

= 0.4

n = 75

Now calculate 99% confidence interval is

CI = x_bar z*(/n)

z value for 99% confidence interval is 2.58

CI = 38.3 2.58*(0.4/75)

= 38.3 0.1192

CI = 38.3 - 0.1192 and CI = 38.3 + 0.1192

= 38.181 and CI = 38.419

Therefore 99% confidence interval is

(38.181, 38.419)

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