Question

Thirty items are randomly selected from a population of 320
items. The sample mean is 29, and the sample standard deviation 3.
Develop a 80% confidence interval for the population mean.
**(Round the t-value to 3 decimal places. Round the
final answers to 2 decimal places.)**

The confidence interval is between and

Answer #1

Solution :

Given that,

t /2,df = 1.311

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

= 1.311 * (3 / 30)

Margin of error = E = 0.72

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

- E < < + E

29 - 0.72 < < 29 + 0.72

28.28 < < 29.72

The confidence interval is between **28.28 and
29.72**

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