PASS 2020 Update

Use the button(s) below to download the PASS 2020 installation file. If PASS 2020 is not yet installed on your computer, this will install the full version. If you already have PASS 2020 installed, this will update your current installation to the newest version. Your personal files will not be affected.

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Current Version: 20.0.3
Released: August 27, 2020

Click here for minimum System Requirements


PDF documentation for PASS 2020 is installed with the software and can be accessed through the Help System. The documentation is also available online by clicking here.

Update Release Notes

This page lists the changes that have been made to PASS 2020 since it was released.

Version: 20.0.3

Released: August 27, 2020

1. Mediation procedures have been corrected to allow for negative value input in all appropriate cases. Before the corrections were made, the sample size search would not converge.

2. Corrected a “value out of range” error that was occurring in the Confidence Intervals for One Proportion in a Stratified Cluster-Randomized Design procedure in some cases when the computer language setting uses comma as the decimal.

3. Corrected an error in the display of input headings for the One-Sample Logrank Tests procedure. The "Alpha" heading was being displayed in error on the panel when the Solve For was set to "Effect Size".

4. Corrected output typos in the two-sided null hypothesis for the Two-Sample T-Tests Assuming Equal Variance procedure, Two-Sample T-Tests Allowing Unequal Variance procedure, and the Mann-Whitney U or Wilcoxon Rank-Sum Tests. The null hypothesis for the two-sided test was incorrectly stated as H0: δ ≠ 0 instead of H0: δ = 0. This error did not affect calculations.

Version: 20.0.2

Released: May 22, 2020

1. Updated the Tests for Two Ordered Categorical Variables procedure to include Odds Ratio input (in addition to Log(Odds Ratio) input) and additional methods for specifying the control group category proportions.

2. Added examples to demonstrate how the Tests for Two Ordered Categorical Variables procedure can be used in planning a clinical trial to assess the effectiveness of a treatment in combatting COVID-19 where the study outcome is based on a multi-category ordinal scale of illness severity.

3. Added an example to demonstrate how the Logrank Tests (Freedman) procedure can be used in planning a clinical trial to assess the effectiveness of a treatment in combatting COVID-19 where the study outcome in each group is the number of days it takes patients to advance two categories on a multi-point ordinal scale of disease status.

4. Corrected an error in the Equivalence Tests for the Ratio of Two Means (Normal Data) procedure. The values of N2 and N were displayed wrong in some cases. Incidentally, N2 is not used in the power calculation, so that value is correct.

5. Corrected an error in the Group-Sequential simulation procedures that required the user to repeatedly press “Abort” in order to Abort a procedure run.

6. Corrected an error in the Cox Regression procedure when solving for power with B = 0. PASS was returning Beta for Power instead of returning Alpha for Power.

7. Corrected an error that caused plots with Extra Symbols added outside the bounds of the plot lines to become tiny. Extra symbols outside of the plot boundaries are not displayed.

8. The validation example (based on Lakatos, 1988) for the Two-Group Survival Comparison Tests (Simulation) procedure and the Logrank Tests procedure had the noncompliance and drop-in rates reversed. This was fixed in the documentation and in the validation example templates. The fix did not result in a change to the estimated sample size.

9. Corrected minor typos in the power formula in the documentation of the Equivalence Tests for the Difference Between Two Correlated Proportions procedure.

Version: 20.0.1

Released: February 10, 2020

1. Initial Release of PASS 2020.

"I purchased NCSS last week and have been extremely impressed with the product so far. The documentation is superb... Especially strong is the importing of files from Excel and other statistics programs..."

Gary Brager, Baltimore County Public Schools

NCSS is an excellent tool for clinical and epidemiological research that is both user friendly and economical with excellent support. It removes the "fear of statistics" from clinical research and makes research accessible to all curious clinicians.

Ted Rosenberg, MD MSc. FRCP(C), Clinical Assistant Professor, University of British Columbia