The purpose of this activity is to use computer simulation to visually explore and reinforce the relationship between confidence and width, for confidence intervals. We will use an applet to explore this concept.

Launch the applet in a separate window.

As you will remember from a previous activity, the applet shows a normal-shaped distribution, which represents the sampling distribution of the mean (x-bar) for random samples of a particular fixed sample size, from a population with a fixed standard deviation (σ, sigma). The green line marks the value of the population mean (μ, mu).

To begin the simulation, click “sample 25” button. You have used the simulation to select 25 samples from the population; the applet has automatically computed the sample means and the corresponding confidence intervals.

Notice, along the left of the applet, that you can change the confidence level. Do this, and watch what happens to the intervals as the confidence is changed among all the levels available.