A level *C* confidence interval for a parameter is an interval computed from
sample data by a method that has probability *C* of producing an interval containing
the true value of the parameter.

In the applet below we will construct a level *C* confidence interval for the
mean (µ) of a population. Set the desired confidence level by clicking on
the radio buttons to the left of the plot. Click the **Sample** button for a single SRS.
Click the **Sample 50** button for 50 SRSs. The dot marks the sample mean, which is
the center of the interval. The lines on each side of the dot span the confidence interval.
The total number of samples and number that "hit" (i.e., confidence interval did not
contain µ) are shown on the right.

© 2009 W. H. Freeman & Co. and Sumanas, Inc.