WinPepi

Origins

WinPepi had its origins in a set of programs for programmable pocket calculators that was published in book form in 1983 with the stated aim of making life easier for investigators, extending the use of appropriate analytic methods, and enabling researchers to concentrate on substantive issues rather than on procedural technicalities. DOS-based adaptations for computer use were published in 1993, and subsequent versions were dubbed “Pepi” (an acronym for Programs for EPIdemiologists). After the fourth version (published in 2001), the programs were amplified and adapted (using the Delphi software development package) for use with Microsoft Windows (Microsoft Corporation, Redmond, WA). New expanded versions were subsequently issued at frequent intervals. The programs are compatible with Microsoft Windows Vista.

Characteristics and Contents

Each program has several modules (more than 100 in all), each of which provides several, sometimes many, statistical procedures. An alphabetical index that lists the available procedures and analyses is supplied; this pinpoints the programs and modules to be used for specific purposes. The programs are accompanied by detailed manuals, which explain the uses and limitations of specific procedures, and furnish formulas and references.

WinPepi is characterized by its versatility. The wide range of procedures that are offered has repeatedly led reviewers to use a “Swiss army [Page 1634]knife” analogy. The suite provides most of the statistical procedures commonly used in epidemiological studies (with some notable exceptions, such as Cox regression analysis and procedures for the study of disease clustering), as well as many that are less commonly used, or not easily found (or not easily found in a user-friendly format). This versatility carries a price because to simplify operation, the programs generally perform all the relevant procedures that the data will permit, without requiring detailed choices by the user, and as a consequence, they generally display many more results than a specific user requires. Students and other users, therefore, have to learn to seek only the results they need and ignore the others. At the same time, the rich output might stimulate an interest in other measures and tests. In many instances, the programs provide alternative tests (both parametric and nonparametric) and alternative measures of effect, often with confidence intervals estimated by alternative methods; 90%, 95%, and 99% confidence intervals are generally provided.

WinPepi is also characterized by its user-friendliness. The programs are easy to install—they are portable stand-alone programs that need only be copied to any chosen folder; no changes are required in the Windows registry. A WinPepi portal program is supplied, providing immediate access to the programs, the manuals, and the alphabetical index listing the available procedures and analyses. This index also can be accessed from the programs. When the selected program has been opened and a module has been selected (which requires the user to know what he or she wants), it is necessary only to click on the required options (if any), enter the data, and click on “Run.” Menus and buttons make the programs easy to use. Simple instructions are shown in every window, and numerous pop-up hints, help screens, error traps, and warning messages are provided, so that it is seldom necessary to seek operating instructions in the manual. The manuals can be accessed from the programs.

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