1. Discussion 2
1/13/2014

2. Outline Confidence limits Power Sample size estimation
One sample
Population variance known or unknown
Two sample
Sample size estimation
One sample (confidence interval)
Two sample (detect differences between two means)
How to read data in SAS

3. Questions?

4. Confidence Limits
If we take repeated samples of size n and construct confidence intervals we can expect (1 – α) x 100% of the intervals to contain the true population mean
Example: n = 14, α = 0.05, and standard error of mean =

5. Power
One sample – detect a difference between a mean and value previously known
If you know population standard error
If you don’t know population standard error

6. Power Two sample – detect a difference between two means
If sample size is different between group1 and group 2
If sample size is the same between group 1 and group 2
If the population variance is given to you, substitute it into the equation instead of the sample pooled variance

7. Sample Size Estimation
One sample – sample size to estimate a confidence interval of a mean
Where
Remember to do iterations when estimating sample size

8. Sample Size Estimation
Two sample – Sample size to detect differences between two means with a give α and power
Where
Remember to do iterations when estimating sample size

9. How to read data in SAS
Looked at correct and incorrect methods to read data in SAS using the data from Lab 1 Example 4