This demonstration allows you to compare the t distribution to the standard normal distribution. When the applet begins, the standard normal distribution is compared to a t distribution with three degrees of freedom. You can change the degrees of freedom of the t distribution with the slider. The 3 and the 50 mark the ends of the slider. The "current" degrees of freedom are shown at the bottom where it says "t distribution with df=3." As you change the slider, the df are shown by this last line. The "zoom in" button allows you to change the scale of the graph to see the tails of the distribution in more detail.