• Demonstrate how to use the margin of error formula (t*(n-1)• S ) to calculate sample size when given a predetermined margin of error and level of confidence for a one-sample t-interval
• Review standard error for means
This packet is similar to the packet on estimating a sample size for proportions. We show you how to calculate a desired sample size given a margin of error and confidence level.
This packet covers sample size estimation when you are given a margin of error and confidence level for a means problem. There is a powerpoint of definitions and examples, as well as examples for you to do on your own. There are no new terms in this packet.
This powerpoint breaks down the sample size estimation formula, and gives a short example of how to use it.
This video shows two examples on estimating a desired sample size based on predetermined margins of error.
Suppose we have a population with a standard deviation of 17. We would like to create a 99% confidence interval with the margin of error being at most 5. What should our sample size be?
For our formula, we have a standard deviation of 17, a multiplier of 2.576(from the powerpoint), and a margin of error of 5. Therefore, we have
n = ((2.576*17)/5)^2 = 8.7584^2 = 76.7096 which we will round up to 77.
Therefore, a sample of size 77 will ensure our margin of error for our confidence interval is no greater than 5.