STATISTICAL TECHNIQUES AND TOOLS
CONFIDENCE INTERVALS
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Question
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354
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355
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Detailed explanation-1: -Question 1105005: Determine the minimum sample size needed to construct a 95% confidence interval for the mean age of employees at a company. The estimate must be accurate to within 0.5 years. Assume the sample standard deviation is 4.8 years. Your preliminary sample will be at least 30.
Detailed explanation-2: -Since 95% of values fall within two standard deviations of the mean according to the 68-95-99.7 Rule, simply add and subtract two standard deviations from the mean in order to obtain the 95% confidence interval.
Detailed explanation-3: -Then we can find the sample size to yield an interval with that confidence level and with a half width not more than the specified one. The crude method to find the sample size: n = ( z / 2 E ) 2 Then round up to the next whole integer.