The Researcher's Tool Kit

Resources for working smarter

Leave a comment

VassarStats: Clinical Research Calculators

Richard Lowry, Ph.D., Professor of Psychology Emeritus from Vassar College has created a site dedicated to the free dissemination of statistical resources.  Its various computational components are programmed entirely in JavaScript   All calculations are performed within your browser. There is no transmission of data back and forth between your computer and the server.cropped-cropped-toolkit-24157707-copy.jpg

The best web browsers for using this site are Firefox, Safari, and Chrome.  Internet Explorer is not recommended.  Explorer will not respond to some of the programming on this site unless you modify the browser’s security settings.

Three (3) Clinical Research Calculators are available.  Go to VassarStats, then choose “Clinical Research Calculators” from the menu shown on the left-sided purple column.   A description for each of the available calculators follows:

Calculator 1. Given a sample of subjects cross-classified according to whether a certain condition is present or absent, and according to whether a test designed to indicate the presence of that condition proves positive or negative, this unit will calculate the estimated population midpoints and 95% confidence intervals for prevalence, sensitivity, specificity, predictive values (probabilities for true positive, true negative, false positive, and false negative), and likelihood ratios.

Calculator 2. Given the prevalence of a condition within the population and the sensitivity and specificity of a test designed to indicate the presence of that condition, this unit will calculate the predictive values of the test (probabilities for true positive, true negative, false positive, and false negative) and its positive and negative likelihood ratios.

Calculator 3. For two groups of subjects, each sorted according to the absence or presence of some particular characteristic or condition, this unit will calculate standard measures for Rates, Risk Ratio, Odds, Odds Ratio, and Log Odds. It will also calculate the Phi coefficient of association and perform a chi-square test of association (for large samples) or a Fisher exact probability test (for small samples).