1. Chapter 12 Inference for Proportions
AP Statistics
12.2 – Comparing Two Population Proportions

2. Conditions for 2-proportion Inference
Both samples were collected by an SRS.
Samples are Independent of each other.
Both populations are at least Ten times the sample.
The distribution of is approximately normal for large sample sizes:

3. Comparing 2 Population Proportions (Note: proportions use Z – Procedures)
We compare population difference by using sample differences
Confidence Intervals:
Significance Tests:
z-statistic:

4. Construct a 95% CI:

5. Common Practice Comparative Studies
Start w/ 1-sample  divide into 2 groups based on data
2-sample z procedures for comparing population proportions are valid in these situations.

6. Pooled Sample Proportion
We don’t pool the sample proportion in OUR calculations, but the calculator does, so you must do the z-statistic by hand!