Question


A simple random sample of 70 items resulted in a sample mean of 80. The population standard deviation is

σ = 15.

(a)

Compute the 95% confidence interval for the population mean. (Round your answers to two decimal places.)

to

(b)

Assume that the same sample mean was obtained from a sample of 140 items. Provide a 95% confidence interval for the population mean. (Round your answers to two decimal places.)

to

(c)

What is the effect of a larger sample size on the interval estimate?

A larger sample size provides a smaller margin of error.A larger sample size does not change the margin of error.     A larger sample size provides a larger margin of error.

Homework Answers

Answer #1

a) At 95% confidence level, the critical value is z0.025 = 1.96

The 95% confidence interval, is

b) The 95% confidence interval, is

c) A larger sample size provides a smaller margin of error.

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