== Power computations ==

Power computations can be performed in SPSS and R ''only'' using syntax. For SPSS users Chris Aberson has syntax for power calculations in his book. See reference below.

For a theoretical background and details of specialist software have a look at graduate seminar on power at the [[StatsCourse2006|Graduate Statistics Programme October-December 2006]]. There is also [[http://homepages.gold.ac.uk/aphome/cc16work.doc|a worked example]] using "Method 2" on a t-test. 

__Sample sizes required for a given power__

 * [[FAQ/power/onesamp|One sample t-test]]

 * [[FAQ/power/unpaired|Unpaired t-tests (equal group sizes)]]

 * [[FAQ/power/unpairedUneq|Unpaired t-tests (unequal group sizes)]]

 * [[FAQ/power/pairt|Paired t-tests]]

 * [[FAQ/power/owAnovaN|Regression including One-Way ANOVA and ANCOVA]]

 * [[FAQ/power/pPowN| Comparing a single proportion with a constant (sign test)]]

 * [[FAQ/power/propsn| Comparing two independent proportions]]

 * [[FAQ/power/prop1sn|Comparing three or more independent proportions]]

 * [[FAQ/power/mcn| Comparing two related proportions (McNemar test)]]

 * [[FAQ/power/FisherrN| Comparing two independent correlations from two different samples]]

 * [[FAQ/power/rmPowN| A term in any Anova (including repeated measures)]]

 * [[FAQ/power/llogN| A single predictor in a multiple binary logistic regression]]

 * [[FAQ/power/hazN| Survival analysis]]


__Power required for given sample sizes__

 * [[FAQ/power/onesampn|One sample t-test]]

 * [[FAQ/power/unpaireqn|Unpaired t-tests (equal group sizes)]]

 * [[FAQ/power/unpairn|Unpaired t-tests (unequal group sizes)]]

 * [[FAQ/power/pairn|Paired t-tests]]

 * [[FAQ/power/owanova|Regression including One-Way ANOVA and ANCOVA]]

 * [[FAQ/power/pPow| Comparing a single proportion with a constant (sign test)]]

 * [[FAQ/power/props|Comparing two independent proportions]]

 * [[FAQ/power/prop1s|Comparing three or more independent proportions]]

 * [[FAQ/power/mcnemarN| Comparing two related proportions (McNemar test)]]

 * [[FAQ/power/Fisherr| Comparing two independent correlations from two different samples]]

 * [[FAQ/power/rmPow|A term in any Anova (including repeated measures)]]

 * [[FAQ/power/llogPow| A single predictor in a multiple binary logistic regression]]

 * [[FAQ/power/haz| Survival analysis]]


Additional power freeware (including the popular G*POWER (currently version 3)) is available  for download from [[http://www.epibiostat.ucsf.edu/biostat/sampsize.html#PCSize|here.]] Some examples using G*POWER 3 are in Howell (2013).

__References__

Aberson CL (2010) Applied power analysis for the behavioral sciences. Routledge:London. This book contains examples of computing effect sizes and power using SPSS.

Howell DC (2013) Statistical methods for psychology. 8th Edition. International Edition. Wadsworth:Belmont,CA.