# Linear Models

• ### Cartoon: The Measurement Machine

A cartoon to teach about the measurement issues of bias, reliability, and validity. Cartoon by John Landers (www.landers.co.uk) based on an idea from Dennis Pearl (The Ohio State University). Free to use in the classroom and on course web sites.
• ### Regression Activity

This activity focuses on basic ideas of linear regression. It covers creating scatterplots from data, describing the association between two variables, and correlation as a measure of linear association. After this activity students will have the knowledge to create output that yields R-square, the slope and intercept, as well as their interpretations. This activity also covers some of the basics about residual analysis and the fit of the linear regression model in certain settings. The corresponding data set for this activity, 'BAC data', can be found at the following web address: http://www.causeweb.org/repository/ACT/BAC.txt

• ### Quote: Asimov on Measurement

... we must remember that measures were made for man and not man for measures. a quote of popular science and science fiction author Isaac Asimov (1920 - 1992) in "Of Time and Space and Other Things" page 143, Avon Books, 1965. The quote also appears in "Statistically Speaking: A dictionary of quotations" compiled by Carl Gaither and Alma Cavazos-Gaither.

• ### Quote: Durand on Degrees of Freedom

The number of degrees of freedom is usually self-evident - except for the analysis of data that have not appeared in a textbook. A quote from M.I.T. professor of management David Durand (1912- 1996) Published in a letter to the editor of "The American Statistician" June, 1970 as part of a tongue-in-cheek "Dictionary for Statismagicians." The quote also appears in "Statistically Speaking: A dictionary of quotations" compiled by Carl Gaither and Alma Cavazos-Gaither.
• ### Cartoon: Butter Usage Results

A cartoon to teach about the Margin of error in sample surveys. Cartoon by John Landers (www.landers.co.uk) based on an idea from Dennis Pearl (The Ohio State University). Free to use in the classroom and on course web sites.
• ### Why Use Multiple Comparison Tests?

This page discusses the proper procedures for multiple comparison tests and reasons behind them.
• ### Song: Natural Log

Song about the use of the logarithmic transformation in statistics. May be sung to the tune of "Hound Dog" which was popularized by Elvis Presley. Lyrics written by Dennis Pearl with assistance from Deb Rumsey. Musical accompaniment realization and vocals are by Joshua Lintz from University of Texas at El Paso.

• ### 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.