Power Analysis &
Sample Size Software

Free TrialBuy Now

PASS Software

PASS software is an easy-to-use research tool for determining the number of subjects that should be used in a study. As the leader in sample size technology, PASS performs power analysis and calculates sample sizes for over 230 statistical tests and confidence intervals. With more sample size options than any other package, PASS is the best research planning tool on the market.

PASS Overview

Click here to view a video demonstration of the use of PASS

Click to see details:   One or Two Means    Multiple Means    Correlation    Normality Tests

Variances and Standard Deviations    Regression    One Proportion

Two Proportions    Chi-Square and Other Proportions Tests    Survival

PASS software contains a large collection of tools for examining power or calculating sample size for a given statistical procedure. Each procedure may be selected from the menu, category tree, or a procedure search.

PASS Home Window

PASS Home Window

Once a procedure is chosen, a procedure window opens for input of the needed power or sample size parameters.

Procedure Window for Two-Sample T-Tests

PASS T Test Procedure Window

On the procedure window, you can select at the top whether you wish to solve for the sample size, power, or some other parameter. As you mouse over each option, helpful definitions and hints are shown at the right. For many of the parameters, a range of values may be entered to examine the effect of changing that parameter. You can also press the help button in the top right corner to see the technical details of the procedure, as well as examples and procedure validation. When the Calculate button is pressed, the output screen appears with the numeric results, article references, report definitions, summary statements, and charts of the numeric results.

PASS Output Window

PASS Output Window

This output can be saved or easily copied-and-pasted to a word processing application. The charts can be saved to a variety of file formats.

Free Trial

Click here for a free trial

We recommend that you download the free trial and open a sample size procedure that interests you. Also, feel free to click on the small help button in the top right corner of any window or procedure to see explanations, examples, and technical details. We are confident that when you try PASS, you will quickly see that it is accurate, easy-to-use, and covers the full range of sample size tools you need.


We have a team of PhD statisticians that are waiting to answer your email or telephone questions. We also have an expanding collection of training videos that are free to view at any time.

New in PASS13

PASS 13 introduces 3D sample size and power curves, as well as improved drop-downs for selecting multiple values. The help center and video help has been expanded. The selection for group allocation in the two-sample procedures has been enhanced. PASS 13 adds over 25 new power and sample size procedures to PASS, including one-way tests (3), variance tests (5), correlation tests (5), correlation confidence intervals (4), exponential distribution parameter confidence intervals (4), quality control (2), Coefficient (Cronbach’s) Alpha confidence interval (1), Kappa confidence interval (1), area under an ROC curve confidence interval (1), Michaelis-Menten parameters confidence intervals (1), and tests for two means in a multicenter randomized design (1). Click here to learn more about what’s new in PASS 13.

Documentation & Validation

PASS comes with complete help system documentation that contains tutorials, examples, annotated output, references, formulas, validation, and complete instructions on each procedure. The documentation is also available online by clicking here. All procedures are validated with published articles or books.