Case 2 - Polling

Find three interesting polls reported in the news media, each of which includes information about the size of the sample, the population proportion found, and the margin of error.

Select your three interesting polls to be quite different, both in subject matter and apparent polling data. In particular, try to find three polls with different sample sizes (n's).

Show and explain the mathematics behind the reported margin of error in each poll. In the process you will be verifying the reported margin of error. [You shouldn't show the detailed arithmetic, but you should show the major steps in the computation as if explaining to a smart person who doesn't happen to know about confidence intervals.]

If you find that the reported margin of error differs from your calculations, and you are sure of your own work, the discrepancy might come from the newspaper using a different confidence level in their confidence interval, e.g., 99% instead of 95%, or 90% instead of 95%, or using 0.5 instead of p-hat in the computation of the standrad deviation of p-hat. You might carry out the computations for one or two of these others to see if you can match the reported margin of error.

Present your work on each of the three polls as if explaining vividly clearly to someone who knows some statistics but isn't too great at the inferential statistics of population proportions and polling.