Confidence Interval for a Proportion

To use the applet below, just type in the information into the boxes.  Hit enter when you are finished typing.  You will need a calculator to work these problems out. 

In the applet, the number of successes is labeled "r", so that p = r/n.

You will also need the table below.

Table for Confidence Intervals

c 0.8 0.9 0.95 0.99
zc 1.28 1.645 1.96 2.58


Written Exercises

When you have mastered the above tutorial, please answer the following in a few complete sentences

  1. What are the steps for determining a confidence interval for a proportion?

  2. If your calculations show that a 95% confidence interval for a proportion is [0.4,0.5], is it possible that the true population proportion is .3?

Information on finding the confidence interval for a proportion

Statistics Lecture Notes

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