The larger the degrees of freedom, the closer the t-density is to the normal density. This reflects the fact that the standard deviation s approaches for large sample size n. You can visualize this in the given applet by moving the sliders.
The seventh chapter of an online Introduction to Biostatistics course. Two sets of lecture notes are provided (only the first one works). Additionally, links for additional reading and exercises with solutions are provided.
By changing the number of degrees of freedom in a t-distribution, students can see how the pdf changes. They also have the option of overlayng the standard normal curve so that they can see the convergence.
This site explains small sample hypothesis testing for a normal population and hypothesis testing for a population proportion. Includes examples and exercises.
