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. Round your answers to one decimal place. ( , ) b. Assume that the same sample mean was obtained from a sample of 120 items. Provide a 95% confidence interval for the population mean. Round your answers to two decimal places. ( , ) c. What is the effect of a larger sample size on the interval estimate? Larger sample provides a - Select your answer - margin of error.
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The formula for SEM is standard deviation divided by the square root of the sample size. For the first sample of 60 items, the SEM is 15 / sqrt(60) = 1.94 (rounded to two decimal places). The 95% confidence interval is calculated as the sample mean plus or Show more…
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