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PS Power and Sample Size

PS is an interactive computer program for performing statistical power and sample size calculations. [1][2][3]

PS Power and Sample Size Calculator
PS Power & Sample Size logo.png
Developer(s)W.D. Dupont & W.D. Plummer
Stable release
3.1.2 / August 2014
Operating systemWindows. Also on Apple and Linux under Wine
TypePower & sample size calculations
LicenseCreative Commons Attribution-NonCommercial-NoDerivs 3.0 United States License


Program descriptionEdit

The PS program can be used for studies with dichotomous, continuous, or survival response measures. The user specifies the alternative hypothesis in terms of differing response rates, means, survival times, relative risks, or odds ratios. Matched or independent study designs may be used. Power, sample size, and the detectable alternative hypothesis are interrelated. The user specifies any two of these three quantities and the program derives the third. A description of each calculation, written in English, is generated and may be copied into the user's documents. Interactive help is available. The program provides methods that are appropriate for matched and independent t-tests,[1] survival analysis,[4] matched[5] and unmatched[6][7] studies of dichotomous events, the Mantel-Haenszel test,[8] and linear regression.[2] The program can generate graphs of the relationships between power, sample size and the detectable alternative hypothesis. It can plot graphs of any two of these variables while holding the third constant. Linear or logarithmic axes may be used and multiple curves can be plotted on each graph. Graphs may be copied and pasted into other documents or programs for further editing.


Reviews of this program have been published by McCrum-Gardner,[9] Thomas and Krebs,[10] Stawicki[11] and Pezzullo.[12]


  1. ^ a b Dupont WD, Plummer WD: "Power and Sample Size Calculations: A Review and Computer Program", Controlled Clinical Trials 1990; 11:116-28.
  2. ^ a b Dupont WD, Plummer WD: "Power and Sample Size Calculations for Studies Involving Linear Regression", Controlled Clinical Trials 1998; 19:589-601.
  3. ^ Dupont WD and Plummer WD: PS power and sample size program available for free on the Internet. Controlled Clin Trials,1997;18:274
  4. ^ Schoenfeld DA, Richter JR: "Nomograms for Calculating the Number of Patients Needed for a Clinical Trial With Survival as an Endpoint" Biometrics 1982; 38:163-170.
  5. ^ Dupont, WD: "Power Calculations for Matched Case-Control Studies", Biometrics, 1988; 44:1157-1168.
  6. ^ Casagrande JT, Pike MC, Smith PG: "An Improved Approximate Formula for Calculating Sample Sizes for Comparing Two Binomial Distributions", Biometrics, 1978; 34:483-486.
  7. ^ Schlesselman JJ: Case-control Studies: Design, Conduct, Analysis. New York: Oxford U. Press; 1982:144-152.
  8. ^ Wittes J, Wallenstein S: "The Power of the Mantel-Haenszel Test" J Am Stat Assoc, 1987; 82:1104-1109.
  9. ^ McCrum-Gardner, E: "Sample size and power calculations made simple." International Journal of Therapy and Rehabilitation. 2010; 17:10-14.[1]
  10. ^ Thomas L, Krebs CJ. "A Review of Statistical Power Analysis Software." Bulletin of the Ecological Society of America. 1997; 78(2):126-39. [2]
  11. ^ Stawicki, SPA: "RESEARCH GUIDE:Guide to free statistical software: General applications." OPUS 12 Scientist, 2010; 4:12-13.[3]
  12. ^ Pezzullo, JC: "Free Statistical Software" [4] Retrieved August 28, 2013

External linksEdit