# StatCalc: Statistical Calculators

StatCalc is a statistical calculator that produces  summary epidemiologic information. The summary data do not need to be contained in an Epi Info™ 7 project or entered in any other tool.

Six types of calculations are available in StatCalc:

• Sample Size and Power calculations include Population Survey, Cohort or Cross-Sectional, and Unmatched Case-Control.
• Chi-square for trend tests for the presence of a trend in studies where a series of increasing or decreasing exposures is being examined.
• Tables (e.g. 2 x 2, 2 x n) – Both single and stratified 2 x 2 tables can be analyzed to produce odds ratios and risk ratios (relative risks) with confidence limits, several types of chi square tests, Fisher exact tests, Mantel-Haenszel summary odds ratios and chi squares, and associated p-values. These calculations are similar to those produced in Classic Analysis and Visual Dashboard.
• Poisson (rare event vs. std.) – A Poisson distribution predicts the degree of spread around a known average rate of occurrence.
• Binomial (proportion vs. std.) – A binomial distribution states the probability of positive outcomes in a two-outcome study (yes/no) based on the number of observations and the expected percent of positive outcomes.
• Matched Pair Case Control Study – calculates the statistical relationship between exposures and the likelihood of becoming ill in a given patient population.

OpenEpi.com – Open source web tool that provides additional epidemiologic statistics.

### Open StatCalc

1. From the Epi Info™ 7 main menu, click he StatCalc button.
Figure 10.1: StatCalc Menu Button
2. Select one of the following tools from the drop-down list: Sample Size and Power, Chi Square for Trend, Tables (2 x 2, 2 x n), Poisson (rare event vs. std.), Binomial (proportion vs. std.) or Matched pair case control study.These tools are also available by pressing the corresponding key on the keyboard that matches the first letter of each option. If you select a tool using the keyboard, the tool appears immediately.

If you select the Sample Size and Power tool, the following options appear: Population Survey, Cohort or Cross-Sectional, Unmatched Case-Control.

Navigate each StatCalc tool using the tab or return key to move through the different cells available for data entry.

3. Enter data for each calculation type. Calculations are performed as data are entered into each cell.
4. To modify values already entered, use the Tab key or click on the cell and enter the new information.

#### Print

All results produced from StatCalc may be printed in Epi Info™ by right clicking and selecting Print from the pop-up menu.

Figure 10.2: Save As Image / Print Menu

#### Save

A screen shot of the results produced from StatCalc may be saved in Epi Info™ by right clicking and selecting Save as Image from the pop-up menu.