# Resource Library

#### Statistical Topic

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• ### Student's T Distribution

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.
• ### Building a Probability Tree Applet

This applet simulates a probability tree diagram. Step 1: Click inside the appropriate box on the desired level to build the tree. Step 2: Click on "Set Probabilities" at the top. Step 3. When you enter the respective probabilities, you must hit the ENTER key after each one. Step 4: Once all of the probabilities have been set (they should be blue), click "Final Tree" Step 5: Click "Simulation".
• ### Introduction to Biostatistics

An online Introduction to Biostatistics course complete with lecture notes and links for futher reading, links to applets, and exercises with solutions given.
• ### Regression/Correlation

The ninth chapter of an online Introduction to Biostatistics course. Lecture notes and links for futher reading are provided.
• ### Summarizing Data

The first chapter of an online Introduction to Biostatistics course. Two lecture notes and a set of overheads are provided. Additionally, links for additional reading and exercises with solutions are provided.
• ### Hypothesis Testing

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.
• ### Construct Validity in Psychological Tests

A paper discussing the development of construct validity as applied to psychological studies.
• ### Comparing Two Groups

This page discusses the procedures and applications of the two sample t test and the paired t test.
• ### Variance and standard deviation

This source defines and explains variance and standard deviation.
• ### Age-Structured Population Growth Applet

This applet allows you to manipulate the starting population, age-class survival rates, and age-class fecundity rates over 10 generations for up to 6 age classes. The default gives you the same population size for each age class as well as the same fecundity rate and survival rates. Move the sliders for each age class to manipulate each of these factors. You will see the relative proportions of each age class will change over time, but will eventually reach a stable age distribution.