Question

In: Statistics and Probability

A simple random sample of 60 items resulted in a sample mean of 10. The population...

A simple random sample of 60 items resulted in a sample mean of 10. The population standard deviation is 20.

Compute the 95% confidence interval for the population mean. Round to 1 decimal place.

Assume that the same sample mean was obtained from a sample of 120 items. Provide a 95% confidence interval for the population mean. Round to 2 decimal places.

What is the effect of a larger sample size on the interval estimate? Larger sample provides a larger or smaller margin of error.

Solutions

Expert Solution

95% confidence interval for is

- Z * / sqrt(n) < < + Z * / sqrt(n)

10 - 1.96 * 20 / sqrt(60) < < 10 + 1.96 * 20 / sqrt(60)

4.94 < < 15.06

95% CI is ( 4.9 , 15.1 )

95% confidence interval for is

- Z * / sqrt(n) < < + Z * / sqrt(n)

10 - 1.96 * 20 / sqrt(120) < < 10 + 1.96 * 20 / sqrt(120)

6.4 < < 13.6

95% CI is ( 6.4 , 13.6 )

larger sample size reduces width of confidence interval.

Larger sample size provide smaller margin of error.


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