How many adults must be randomly selected to estimate the mean FICO score of working adults in the United States given the following information
The sample mean should lie within 3 points of the population mean with a 95% confidence interval and the population standard deviation is 68.
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The population standard deviation is 68. The number of people that need to form part a sample if the sample mean should lie within 3 points of the population mean with a 95% confidence interval has to be determined.
Using the central limit theorem approximately 95% of the sample means will fall within 1.96 standard errors of the population mean.
`1.96*(sigma/sqrt n) = 3`
As `sigma = 68`
`1.96*(68/sqrt n) = 3`
=> `sqrt n = (1.96*68)/3`
`n ~~ 1974`
The number of adults that must be randomly selected to estimate the mean FICO score is approximately 1974.
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