# Resource Library

#### Statistical Topic

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• ### DIG Stats: Coliform Activity

In this activity, students will perform a t-test to see if fecal coliform counts collected from Blackwater Creek in Lynchburg, Virginia differ before and after rain showers. Questions about the exercise and links to Excel and TI-83 instructions are given. The data exist in Excel, TI-83, and text formats.
• ### DIG Stats: Seed Harvester Ant Activity

In this activity, students will calculate confidence intervals for the mean weight (in milligrams) of seed harvester ants for 4 size classes of the ants. Questions about the exercise and links to Excel and TI-83 instructions are given. This data exists in Excel, TI-83, and text formats.
• ### Instructor Reputation and Teacher Ratings

This case study covers the concepts including: boxplots, stem and leaf displays, two-sample t tests, and analysis of variance. It also assesses the question, "Does an instructor's reputation affect ratings of the instructor's lecture?"
• ### Regression to the Mean

This is a simulation illustrating the regression toward the mean phenomenon.
• ### Histograms, Bin Widths, and Cross Validation

This applet demonstrates how a histogram is affected by bin width and starting point of first bin. It also illustrates cross-validation criterion for assessing histograms.
• ### Chi Square Test of Deviations from Expected Frequencies

The applet allows users to sample from a normal distribution or from a uniform distribution. It shows the expected values and the observed values and computes the deviation. Then, a chi-square test shows if the deviations are significant for both the normal and uniform distributions.
• ### Video: Against All Odds: 26. Small Sample Inference for One Mean

In this free online video, students discover an improved technique for statistical problems that involves a population mean: the t statistic for use when sigma is not known. Emphasis is on paired samples and the t confidence test and interval. The program covers the precautions associated with these robust t procedures, along with their distribution characteristics and broad applications."
• ### Relative Risks and Odd Ratios

This site provides a PowerPoint presentation of a lesson and examples of relative risks and odds ratios.
• ### Engineering Statistics Handbook

The goal of this handbook is to help scientists and engineers incorporate statistical methods in their work as efficiently as possible.
• ### Kolmogorov-Smirnov Goodness-of-Fit Test (Engineering Statistics Handbook)

This page, part of the NIST Engineering Statistics handbook, describes the Kolmogorov-Smirnov goodness of fit test. It contains a graph of the empirical distribution function with the cumulative distribution function, a definition of the test, the questions it answers, the assumptions that it makes, and links to other goodness of fits tests and a case study.