Posted by **TIMBERLY** on Thursday, April 7, 2011 at 5:35pm.

A simple random sample of 60 items resulted in a sample mean of 80. The population standard deviation is 15.

a) Compute the 95 % confidence interval for the population mean.

b) Assume that the same sample mean was obtained from a sample of 120 items. Provide a 95% confidence interval for the population mean.

c)What is the effect of a larger sample size on the margin of error?

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**PsyDAG**, Saturday, April 9, 2011 at 11:52am
a) 95% = mean ± 1.96 SD

b) 95% = mean ± 1.96 SEm

SEm = SD/√(n-1)

c) margin of error decreases.

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**Anonymous**, Wednesday, June 6, 2012 at 4:07pm
xz

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**Liyyah**, Wednesday, October 28, 2015 at 6:36pm
I would really like to know this answer, i am not good at doing the calculations....can someone help please?

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