1. DRILL What conditions need to be met when doing an inference test?
What is the difference between a Binomial and Geometric Distribution?
If a sample of 200 people showed 34% of the people liked the color blue, how many people like the color blue?
AP Statistics, Section 12.1

2. Section 12.1 Inference for a Population Proportion
AP Statistics
March 22nd 2011

3. Parameters vs Statistics
Mean
Standard Deviation σ
Proportion p
Statistics
Mean
x-bar
Standard Deviation s
Proportion
p-hat
AP Statistics, Section 12.1

4. What we know about inference
We are trying to make sense about what is happening at the population level by looking at sample data
Step 1: “What is the population and the parameter of interest?”
We make assumptions in the form of H0
Step 1: “What is H0?”
We need to know about the distribution of the sample statistic
Step 2: “Is the distribution of sample means normal?”
AP Statistics, Section 12.1

5. Our inferential work so far…
Has been about the distribution of sample means and the distribution of the difference of sample means.
AP Statistics, Section 12.1

6. But what about proportions?
We learned in Chapter 9 about the distribution of sample proportions.
AP Statistics, Section 12.1

7. But what about proportions?
We know that the distribution of sample proportions is approximately normal when these conditions are met…
np>10
nq>10
AP Statistics, Section 12.1

8. AP Statistics, Section 12.1

9. Test of significance
A recent study concluded that 25% of all U.S. teenage females have a STD.
(This is made up) A recent sample of 500 female teenagers from southeastern Oakland county found the 22% have an STD.
Is this strong evidence to suggest that teenage females from SE Oakland county have a lower infection rate than the national average?
AP Statistics, Section 12.1

10. 1: Population, Parameter of Interest, H0 and Ha
3: Calculations
Pop/Parameter: Proportion of teenage girls from southeastern Oakland county with an STD.
2: Procedure Name & Conditions
4: Interpret
1-Prop Z-Test
SRS: Random but not SRS Proceed with caution!
Normality: np & n(1 – p) > 10
Independence: Yes
AP Statistics, Section 12.1

11. Confidence Intervals
AP Statistics, Section 12.1

12. Calculate the Confidence Interval
1: Population & Parameter of Interest
3: Calculations
2: Procedure Name & Conditions
4: Interpret
AP Statistics, Section 12.1

13. Exercises
all
AP Statistics, Section 12.1