Confidence Intervals for Proportions

Confidence intervals for proportions are commonly quoted in news reports for polls, typically as the “margin of error, 19 times out of 20.” In this video we’ll see how a confidence interval for a proportion is constructed, to give a range of plausible values for the proportion in the population or the theoretical world based on the estimated proportion we’ve observed in the real world.

Stream the video without the embedded quiz questions by clicking on the video link below. Closed captions are available.

Notes on the video: Confidence Intervals for Proportion

A point to consider for this video:

Substituting 1/2 for p in the margin of error of a confidence interval is one way to deal with the fact that we don’t know the theoretical world proportion. Why might substituting in the estimated value of p be preferred?