1. 7.3: Confidence Intervals and Sample Size for Proportions
By the end of class you will be able to calculate confidence intervals for proportions

2. Hershey Kisses or Diamonds?
What proportion of times does a Hersey Kiss land on it’s “side” when flipped? Create a 90% confidence interval for this situation.

3. Some Notation:
p = population proportion

4. The sample proportion is the best point estimate for the population proportion
We will conduct 20 trials to get a sample proportion

5. Proportion Confidence Interval
Standard Deviation:
Error:
CI:

6. On Calculator:
Menu
Statistics
Confidence Intervals
1PropZ Interval

7. A sample of 500 nursing applications included 60 men
A sample of 500 nursing applications included 60 men. Find the 90% confidence interval of the true proportion of men who applied to the nursing program.

8. In a sample of 80 high school students, 90% believe that they should be exempt from final exams. Find a 95% confidence interval for students who believe in exam exemptions.

9. Determining Sample Size
According to a prior study .169 is the proportion of people that rent beach umbrellas in Ocean City.
How many beachgoers should be surveyed about umbrella rentals in order to be 90% confident that the sample percentage is in error by no more than 4 percentage points?

10. Determining Sample Size-Solve for n Always round up to ensure the sample size is large enough!

11. If no approximation of the sample proportion is known, use .5 for p-hat. This will guarantee that the sample size is large enough

12. Determining Sample Size
How many beachgoers should be surveyed about umbrella rentals in order to be 90% confident that the sample percentage is in error by no more than 4 percentage points?
No prior sample exists