Statistics
Activity:
Estimating a Population Proportion
Posted on May 12, 2008
Topic: Sampling Distributions
In this activity, students find the confidence interval for a population proportion by first finding the critical value and the margin of error. Finally, they use two formulas for finding the required sample size for a survey, given a confidence interval and margin of error.
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Activity Key Steps:
In problem 1, students explore and create a confidence interval and margin of error for a sample. They first, compute the sample proportion, create a margin of error, and then a confidence interval.
Students are to find the critical value, the margin of error, and the intervals at both the 95% and 99% level. Critical values are found by using invNorm to find the area to the left of that value. The command can be typed, chosen from the Catalog, or found by pressing MENU > Statistics > Distributions > Inverse Normal.
A sample answer students may give is:
The percentage of voters that support the bill is about 87.3%, with a margin of error of plus or minus 3.9%. Or, We are 99% confident that the true percentage of voters that support the bill is between 78.6% and 88.8%.
Students can then use their handheld to compute the Confidence Interval without finding critical value and margin of error. They will be able to check their work by pressing MENU > Statistics > Confidence Intervals > 1-Prop z Interval, then enter x, n, and the confidence level.
At the end of this activity, students will be able to find the confidence interval for a population proportion by first finding the critical value and the margin of error.