# Observational Studies

• ### Two Sample Tests

This lesson introduces two sample hypothesis testing for means and discusses the one-tailed and two-tailed t-tests.
• ### Polls: What Do the Numbers Tell Us?

This tutorial opens with a survey on polling. Upon completing the survey, students are taken through an election example which uses polling to explain random sampling, bias, margin of error, and confidence intervals.
• ### Probability and Statistics Journals on the Web

This site contains links to journals on probability and statistics published around the world. "Some publishers require registration to browse abstracts. Others require a current subscription to the journal by you or your institution. Most browsable titles, abstracts and papers are only for the past year or so."
• ### Quote: Brinner on Anecdotes

The plural of anecdote is not data. Attributed to American economist Roger E. Brinner in the on-line list of quotes at www.keypress.com/fathom/fathom1/quotes.html
• ### Quote: Letterman on Percentages

USA Today has come out with a new survey - apparently three out of four people make up 75 percent of the population. Quote from comedian and late night talk show host David Letterman (1947 - ).
• ### Joke: the number of offspring

Statistics play an important role in genetics. For instance, statistics prove that the number of offspring you will have is an inherited trait. If your parents didn't have any kids, odds are you won't either. Joke #137 of Gary Ramseyer's "First Internet Gallery of Statistics Jokes" contributed by Hugh W. Graham of Abbott Labs.
• ### Cartoon: Question Time

A cartoon to use at the end of a class period when the instructor was rushed to finish. 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.
• ### Quote: Knebel on smoking and statistics

It is now proved beyond doubt that smoking is one of the leading causes of statistics. Quote found in "Reader's Digest" (December, 1961) by journalist Fletcher Knebel (1911-1993)
• ### Song: Scientific Method Blues

Song is an informal overview introducing the conceptual steps of the scientific method. Recorded on the CD "Science Songs and Stories For the Big Questions", available at www.kathleencarroll.com.
• ### Making Students Aware of Bias

The following exercise can illustrate the problem of bias in estimators to students in statistics courses. In some advanced courses an alternative estimator may be presented and properties of this estimator may be investigated via Monte Carlo studies.