Once this value has been entered, the remaining cells are automatically populated. Since 5% is rather low, we will use 9% instead. We already know from literature that this value lies between 5% to 30% (NAFLD in general population). Step 4: Supplying the percentage of outcome among unexposed. Performing the calculation (30/70), one obtains a value of 0.4- this is supplied in the appropriate cell. Among them, those without NAFLD would be around 30%, while those with NAFLD would be around 70%). In the present example, the ratio is approximately 30:70 (The study population will consist of CAD patients. If the proportion of unexposed will be less than the number of exposed, the value will be less than one. Here, one must provide a single value, not ratios (1 not 1:1). Step 3: Supplying the ratio of unexposed to exposed individuals. Increasing the value will increase the sample size. Therefore, we click on the drop-down menu and choose 95% instead. The default value is 99.9%, but this may inflate the estimate. Step 1: Selecting the desired confidence level. Having obtained all the information required, we can now proceed with sample size estimation. The above study is from South Korea, so we must try to obtain literature from India for better estimation.ī. The proportion of NAFLD among CAD patients is reported to be between 69.2% to 80.4% The proportion of NAFLD in the general population is reported to be between 5 to 30% the proportion of NAFLD among patients with CAD.the proportion of NAFLD in the general population.In this case, we need to determine two values: These need to be determined from literature. Obtaining the values for sample size calculationĪlthough we already know what values to supply for confidence level and power, other values are unknown. The values of Odds Ratio and Risk ratio will be populated automatically based on the other values supplied.ī. % outcome in exposed group: the proportion of exposed people with the outcome of interest (in this case, the proportion of CAD patients with NAFLD) % outcome in unexposed group: the proportion of unexposed people with the outcome of interest (in this case, the proportion of general population with NAFLD) Ratio of unexposed to exposed: depends upon the outcome of interest and study population In order to calculate sample size using Epi Info 7, one requires to provide the following information (shown in red): Requirements for calculating sample size using Epi Info 7 (cross-sectional studies) Step 3: Select Cross Sectional Study from the options (shown in red)ī.3. Step 2: Select StatCalc from the menu of options (shown in red) Step 1: Launch Epi Info 7 (please watch video above on downloading and installing Epi Info 7) Launching Cross-Sectional Study within Stat Calc tool of Epi Info 7 Similarly, the exposure is CAD (those who have CAD are ‘exposed’)īy extension, those without CAD (general population) would constitute the ‘unexposed’ group.Īs the investigator wishes to determine the prevalence of NAFLD, the appropriate study design is a cross-sectional study (cross-sectional studies are also called ‘prevalence’ studies).ī. Since one intends to determine the prevalence of NAFLD among CAD patients, the outcome of interest is NAFLD Therefore, the study population is patients with CAD. The investigator wishes to determine the prevalence of Non-Alcoholic Fatty Liver Disease (NAFLD) among persons with Coronary Artery Disease (CAD). If you want to view the video providing instructions on downloading the software, you may do so here. The CDC has produced several tutorial videos for Epi Info 7 that can be viewed here. It also includes a tool for sample size calculation. It provides for easy data entry form and database construction, a customized data entry experience, and data analyses with epidemiologic statistics, maps, and graphs for public health professionals who may lack an information technology background. The latest version of Epi Info is Epi Info 7. Background Information:Įpi Info™ is public domain set of software tools developed by the United States’ Centers for Disease Control and Prevention (CDC) for use by public health professionals and researchers. I believe many more would benefit from a public response, hence this article. Recently, someone asked a question that involved calculating sample size with Epi Info 7. Compare to AcaStat which also provides many of StatCalc's summary statistic procedures.I receive a lot of queries regarding sample size calculation for this article. Output is stored in an output log to view and print results. StatCalc includes example data for each module to help you quickly learn the procedures. A Decision Tools module is included to explore price elasticity of demand, queuing theory, constant dollars, and decision tables. Enter data to create descriptive, correlation, and regression statistics. Use StatCalc to compare summary statistics, develop confidence intervals, and verify hand calculations.
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