Epi Info: Analysis Tool

One of the important tools that the Gorgas Memorial Institute uses to register and analyze data, is called Epi Info. Epi Info is public domain statistical software for epidemiology developed by Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia (USA).

Epi Info has been in existence for over 20 years and is currently available for Microsoft Windows. The program allows for electronic survey creation, data entry, and analysis. Within the analysis module, analytic routines include t-tests, ANOVA, nonparametric statistics, cross tabulations and stratification with estimates of odds ratios, risk ratios, and risk differences, logistic regression (conditional and unconditional), survival analysis (Kaplan Meier and Cox proportional hazard), and analysis of complex survey data. The software is in the public domain, free, and can be downloaded from http://www.cdc.gov/epiinfo. Limited support is available.

 

Features

From a user's perspective, one of the most important functions of Epi Info is the ability to rapidly develop a questionnaire, customize the data entry process, quickly enter data into that questionnaire, and then analyze the data. For epidemiological uses, such as outbreak investigations, being able to rapidly create an electronic data entry screen and then do immediate analysis on the collected data can save considerable amounts of time versus using paper surveys.

Epi Info uses three distinct modules to accomplish these tasks: MakeView, Enter, and Analysis. Other modules include the Report module, a mapping module, a menu module, and various utilities such as the NutStat program.

Electronic questionnaires, also known as "views" in Epi Info terminology, are created in the MakeView module. Individual questions can be placed anywhere on the screen and across multiple pages, with the user given complete control over appearance and function. The user defines both the question's prompt and the format of the data that is to be collected. Data types include numbers, text strings, dates, times, and yes/no. Users can also create drop-down lists, code tables, and comment legal fields. One of the more powerful features of MakeView, however, is the ability to create "check code". Check code allows for certain events to occur depending on what action a data entry person has taken as they are typing. For example, if a user enters "Male" into a question on gender, any questions relating to pregnancy might then be hidden. Skip patterns can also be created so that if a user enters "No" to a question on whether or not they smoke, the cursor skips past any fields related to smoking. Relational database modeling is supported, as users may link their view to any number of other views in their database.

The Analysis module is where users analyze their data. Import and export functions exist that allow for file types to be converted between plain-text, CSV, Microsoft Excel, Microsoft Access, dBase, FoxPro, and other formats. Many advanced statistical routines are provided, such as t-tests, ANOVA, nonparametric statistics, cross tabulations and stratification with estimates of odds ratios, risk ratios, and risk differences, logistic regression (conditional and unconditional), survival analysis (Kaplan Meier and Cox proportional hazard), and analysis of complex survey data.

Using the Epi Map module, data can be displayed either by geographic reference or by GPS coordinates. The Report module allows the user to edit and format output from various Epi Info tools and modules. The resulting HTML document can then be printed or emailed to others.