LARGE SAMPLE CONFIDENCE INTERVAL FOR A PROPORTION APPLET

INSTRUCTIONS

Once the applet has finished loading, a "Compute CI" and a "Graphical CI" button will appear on the screen. This may take a minute or two depending on the speed of your internet connection and computer. Please be patient. If no begin button appears, it is probably because your browser does not support Java 1.1.

Starting the Applet and setting the conditions

1) Press the "Compute CI" button to start the applet in another window.

This applet is an easy-to-use Confidence Interval Calculator. Once the user inputs the sample size, sample proportion, and selects the confidence interval to be calculated(95% or 99%), clicking on the Execute button will compute the large sample CI for a proportion.

2) Press the "Graphical CI" button to start the graphical version of applet in another window.

This applet simulates sampling from a population with true proportion of one half. For each sample, the 95% and 99% confidence intervals on the proportion are computed based on the sample proportion and sample size. The intervals for the various samples are displayed by horizontal lines. If the 95% or 99% confidence interval does not contain the population proportion (one half), it is shown in red. If it contains the population proportion, it is shown in green.

The CI limits for a sample size between 5 and 30 can be obtained on the graph by moving the slider bar. Also specify whether 95% or 99% confidence interval is needed by selecting the appropriate checkbox. For example, selecting a sample size of 5 and 95% CI would imply that 100 samples of sample size 5 would be taken from the large population and the resulting 100 confidence intervals will be plotted.
The cumulative number of confidence intervals containing and not containing the population parameters is tallied.