Question
Find a sample size given a confidence interval, knowing the standard deviation:
Suppose we want to know the average age of the students on a particular college campus, plus or minus .5 years. We’d like to be 99% confident about our result. From a previo us study, we know that the standard deviation for the population is 2.9 years.
1. z a/2 = CI/2 = .99 / 2 = .495 and z-score (.495) = 2.58
2. z score x SD = 2.58 × 2.9 = 7.482
3. Step 2 / margin of error: 7.482 / .5 = 14.96
4. Square Step 3: 14.96 × 14.96 = 223.8016

So we need a sample of 224 people

Question
Find a sample size given a confidence interval, knowing the standard deviation:
Suppose we want to know the average age of the students on a particular college campus, plus or minus .5 years. We’d like to be 99% confident about our result. From a previo us study, we know that the standard deviation for the population is 2.9 years.
?

Question
Find a sample size given a confidence interval, knowing the standard deviation:
Suppose we want to know the average age of the students on a particular college campus, plus or minus .5 years. We’d like to be 99% confident about our result. From a previo us study, we know that the standard deviation for the population is 2.9 years.
1. z a/2 = CI/2 = .99 / 2 = .495 and z-score (.495) = 2.58
2. z score x SD = 2.58 × 2.9 = 7.482
3. Step 2 / margin of error: 7.482 / .5 = 14.96
4. Square Step 3: 14.96 × 14.96 = 223.8016

So we need a sample of 224 people
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owner: naxplast06 - (no access) - Deviant S. - The Practically Cheating Statistics Handbook (2010, CreateSpace Independent Publishing Platform).pdf, p110

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