Sample Size Determination in an Epidemiologic Study using the EpiTools Web-Based Calculator

Romeo L. Villarta, Jr. and Abubakar S. Asaad

Department of Epidemiology and Biostatistics, College of Public Health,
University of the Philippines Manila

Objectives. To evaluate the utility of using a web-based sample size calculator in the preparation of a research proposal.

Methods. EpiTools, a free web-based calculator for sample size determination, was used in various study guides.

Results. Computations of sample size needed for several simple epidemiologic study designs were calculated using different assumptions. The calculator was straightforward to use and user-friendly. The results were calculated quickly. Comparison of the computed sample size using different assumptions may be done to assist in evaluating research project feasibility. The input data and output of the sample size calculation may be transformed into a report for inclusion in the written research proposal.

Conclusion. The EpiTools web-based calculators is a convenient tool for sample size determination in the design of research protocols in relatively simple study designs. It may be used in evaluating the feasibility of the computed sample size needed by the study design.

Key Words: sample size, internet, software