t Distribution Demo

Questions to be answered before the simulation are not yet implemented in this test version.


Begin by answering the questions, even if you have to guess. The first time you answer the questions you will not be told whether you are correct or not.


Once you have answered all the questions, answer them again using the simulation to help you. This time you will get feedback about each individual answer.


General Instructions


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.


Step By Step Instructions


1. Notice the difference in shapes between the standard normal and the t distribution. Which has more scores in the middle? Which has more scores in the tails?


2. Increase the degrees of freedom to 10 (the degrees of freedom are shown on the last line.) Is there still a difference between the distributions. Zoom in to look closely at the tails.


3. Repeat step 2 with 20 degrees of freedom and then with 50 degrees of freedom.


Summary


The t distribution has more scores in the tails than the normal distribution. As the df increases, the difference between the distributions decreases. Differerence between the distributions are more pronounced in the tails then in the middle.