# statistics

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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1. 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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2. xz

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3. I would really like to know this answer, i am not good at doing the calculations....can someone help please?

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4. How do you get 1.96

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