Statistically Significant Sites  by Amy Fluet

Not long ago, I worked with a statistical powerhouse. She can list tests and assumptions and discuss statistical theory without missing a beat. Not all scientists possess such stats expertise, though, and it's not even necessary today. Depending on the field in which you work, you might never run into anything more difficult than a simple t-test. But when it comes to presenting your data, or reviewing someone else's, it can help to have a ready reference at your fingertips. Before you run out and spend money on a textbook or send email to a colleague in the next department, take a look at what the Web has to offer.

Just like teachers in many other fields, statisticians have discovered the advantages of developing online textbooks. Although often designed for introductory undergraduate courses, these sites provide easy-to-locate, nontechnical statistical information for researchers. Many stats sites use Java applets, either to demonstrate principles or to perform calculations. Most of the demonstration applets will be beyond the needs of a busy scientist looking for a quick reference, and they might or might not work on your Internet browser. A few applet-filled sites are listed in this article's endlinks, though, for those who are curious.

A New View of Statistics, an extensive textbook by Will Hopkins of the University of Otago in New Zealand, is probably the easiest to read of these online resources. Hopkins uses a conversational writing style - not equations - to describe concepts. As he says in his preface, "Let's leave the computations to the computers!"

In the frames version, the index is always accessible in the navigation window. From each page it is easy to return to the home page - which has a shortened contents section and a list of updates - or to the full contents. Hopkins chose most of his examples from the field of exercise physiology, but this doesn't limit the usefulness of this resource for scientists from other fields.

Hopkins starts with the very basics, including Summarizing Data: Simple Statistics & Effect Statistics and moves on to discuss more complex statistics, including multiple linear regression. The site also includes discussions of sample size estimation and other subjects of interest to researchers. His topics pull you in because some of them have the air of opinion pieces, including MEAN ? SD or MEAN ? SEM?, which discusses which one you should publish.

The Electronic Statistics Textbook from StatSoft, makers of the Statistica software package, lies at the opposite end of the spectrum, stylistically speaking. This Web site offers plenty of useful information - written in a technical and sometimes dry manner - for both statistically naive and experienced scientists.

The site might have a special appeal for scientists in specific fields, because it covers some rather rare statistical topics, including neural networks and cluster analysis. Selecting the latter topic lets the reader learn about the general nature of cluster analysis or read a more detailed description covering linkage rules and different algorithms used in these analyses.

Topics covered by this site include hypertext words that link to the Statistics Glossary, which is also accessible from the handy navigation window. If you don't see the topic you're looking for in this window, try the site's search engine.

Right below the search engine button is the Statistical Advisor. This online decision tree is a good reference for those without a local stats expert. A researcher might have tons of stats tests on a computer, but which test is the right one?

The Statistical Advisor leads visitors through a series of questions. Each layer of questions grows more specific, ultimately leading to the chapters in the textbook that discuss the relevant tests. You can always select the Get More Info link to learn more about the questions being asked. Visitors need some basic understanding of statistics before beginning a session with the advisor, but the descriptions are written clearly and refer back to specific sections in the online text.

One more online textbook worth mentioning is HyperStat Online, which was developed by David Lane of Rice University. This site is one component of the Rice Virtual Lab in Statistics. This introductory-level text provides several features that make it especially well organized and easy to navigate.

The small navigation bar at the top of the window takes a visitor back to the table of contents with one click. At the start of each of the 18 topics listed in the table of contents is a list of links to other sites that relate specifically to the subject at hand. The glossary quickly loads a list of alphabetical terms.

Selecting a word from the list, for example kurtosis, brings up its detailed definition. Two other useful sites for researchers are Pitfalls of Data Analysis and Intuitive Biostatistics: Choosing a Statistical Test. Both of these easy-to-read pages deal, in a relatively short fashion, with more specific topics. The former was written by Clay Helberg, currently an SPSS employee. The latter is a chapter from a book by Harvey Motulsky, president of GraphPad Software.

After you've perused your favorite online stats text, Interactive Statistical Calculation Pages can get you started with the actual data analysis. This site claims to have over 300 links to Web pages that perform statistical calculations.

John Pezzullo of Georgetown University did a nice job of organizing and annotating these sites. He also noted which sites use JavaScript or Java applets. Pezzullo's own Probability Distribution Functions serves as a quick and easy way to find exact p-values or to look up a critical value for a given p-value. From one page you can find the normal, student t, chi-square, or Fisher F distribution.

Sometimes being knowledgeable is more a matter of knowing where to look things up than actually knowing them off the top of your head. With a few stats sites bookmarked in your Web browser, you'll be able to hold your own when the conversation next turns to p-values and Poisson distributions.

Amy Fluet is a freelance science writer based in Boulder, Colorado.

EndNotes:

Biostatistics Links: Advanced - GraphPad's list of recommended resources, both online and off. They also have a basic list of links.

Instructional Demos - a collection of applets from HyperStat Online. Covers many topics, from descriptive statistics to significance testing.

Java Applet Hotlist - from an online text for introductory statistics. Supplies several examples.

Java Applets - from the Institute of Statistics and Decision Sciences at Duke University. It covers many topics, from t-tests to Z scores.

Statistics and Statistical Graphics Resources - a collection of annotated links including many to software-related sites.

Statistics on the Web - a nicely annotated list of links to statistical professional groups, educational resources, publications, software, and more.

SurfStat australia - designed for the Statistics 101 students at the University of Newcastle in Australia. Another good introductory online text.

Web sites mentioned in this article: