# Simulation

• ### Primer on Interpreting Surveys

Because surveys are increasingly common in the medical literature, readers need to be able to critically evaluate the survey method. Two questions are fundamental: 1) Who do the respondents represent? 2) What do their answers mean? This lecture example discusses survey sampling terms and aspects of interpreting survey results.
• ### Kruskal-Wallis Test

This tutorial on the Kruskal-Wallis test includes its definition, assumptions, characteristics, and hypotheses as well as procedures for graphical comparisons. An example using output from the WINKS software is given, but those without the software can still use the tutorial. An exercise is given at the end that can be done with any statistical software package.
• ### Parametric and Nonparametric Statistics

This page discusses the differences in parametric and nonparametric tests and when to use then.
• ### Why Use Multiple Comparison Tests?

This page discusses the proper procedures for multiple comparison tests and reasons behind them.
• ### Introduction to Probability

This website is provides an online text version of Grinstead & Snell's "Introduction to Probability" as well as supplemental reference information.

• ### Body Measures: Exploring Distributions and Graphs Using Cooperative Learning

Using cooperative learning methods, this lesson introduces distributions for univariate data, emphasizing how distributions help us visualize central tendencies and variability. Students collect real data on head circumference and hand span, then describe the distributions in terms of shape, center, and spread. The lesson moves from informal to more technically appropriate descriptions of distributions.
• ### Understanding the standard deviation: What makes it larger or smaller?

Using cooperative learning methods, this activity helps students develop a better intuitive understanding of what is meant by variability in statistics. Emphasis is placed on the standard deviation as a measure of variability. This lesson also helps students to discover that the standard deviation is a measure of the density of values about the mean of a distribution. As such, students become more aware of how clusters, gaps, and extreme values affect the standard deviation.
• ### Brownian Motion Applet

This applet draws one-dimensional Brownian motion. Click the mouse in the window to start zooming. Click again to stop. Since Brownian motion is self-similar in law, all of the zoomed pictures look the same.
• ### Analysis Tool: HyperStat Online Statistical Analysis (Descriptive Statistics)

This page computes a variety of descriptive statistics and creates a stem and leaf plot. Enter data in the text area, specify a delimiter (Space, Return, Tab, New line), and click "Compute". The page returns sample size, mean, median, trimmed mean, trimean, minimum, maximum, range, first quartile, third quartile, semi-interquartile range, standard deviation, variance, standard error of the mean, skew, and kurtosis. Key Word: Calculator; Summary Statistics.

• ### Gamma Process Applet

This applet draws a Gamma process (a stochastic process with independent increments X(s + t) - X(s).) Click the mouse in the window to start zooming. Click again to stop. The total increase occurs at a countable set of jumps. The simulation gives some idea of this.