1. Chapter 25: Paired Samples and Blocks
AP Statistics

2. Paired/Matched Samples
This situation arises when your groups are NOT independent.
What are common situations where this occurs
Compare subjects with themselves before and after treatment
Compare subjects with themselves on different variables
NEED TO THINK!!!!!!!!!!

3. Logic
If the groups are not Independent, you CANNOT use a 2-Sample Test for Means (2-Sample t-Test)
If the groups are Paired/Matched, you are looking at the differences in the variables and that mean difference
Since you are now only looking at one variable (difference in variables), you will perform a one-sample t-test.

4. Intervals and Tests
When you groups are paired/matched, the intervals you create and the tests you perform are IDENTICAL (mostly) to the intervals you create and the tests you perform for ONE-SAMPLE T-INTERVAL and ONE-SAMPLE T-TEST

7. Assumptions/Conditions
Independence Assumption:
Randomization Condition
10% Condition
Normal Population Assumption:
Need to check each group for normality. SHOW GRAPH.
Nearly Normal Condition
Paired Data Assumption
Check reasonableness of this claim. BE CAREFUL

8. Things to remember It is about the differences in the variables
The null hypothesis is typically written as:
Once you start the “mechanics” of the problem, you will be looking at things like
You are still dealing with a t-model
Don’t use a two-sample t-test for paired data.
Don’t use a paired –t method when the data are not paired

9. Calculator Help
For a paired t test, use the same application as for a one-sample t-test or one-sample t-interval.