Power Calculation, Two Means, t-Test, Independent Samples

Power calculation for independent samples t-tests with option for charts of power vs. sample size (assuming equal sample sizes), sample 1 size, sample 2 size, standardized effect size, and alpha level

General

Element Name Description
Sample One Size Sample size of group one for the power calculation (acceptable range 2 to 150000).
Sample Two Size Sample size of group two for the power calculation (acceptable range 2 to 150000).
Mu1 Population number one mean.
Mu2 Population number two mean.
Population Standard Deviation Standard deviation of the population.
Alpha Level Alpha level (Type I error rate for t-statistic) (acceptable range 0.0001 to 0.25).
Hypothesis type Hypothesis type selection: Two-tailed (Mu1=Mu2, population one mean=population two mean); One-tailed (Mu1<=Mu2, population one mean <= population two mean); One-tailed (Mu1>=Mu2, population one mean >= population two mean).
Detail of computed results reported Output level of detail selection: Power Calculation produces Power Calculation Spreadsheet; Pwr Calc plus Charts option produces, in addition, Power vs. Sample Size (assuming equal sample sizes), vs. Sample Size 1, Vs Sample Size 2, vs. Standardized Effect, and vs. Alpha Level charts.

Chart Parameters

Element Name Description
Number of Steps. (For charts only) Number of individual steps for which to calculate power between the starting and ending parameter values for Power Charts (Min 4, Max 100).
Starting Sample Size. (For charts only) Initial sample size for calculation of all Power vs. Sample Size charts. (Power vs. N chart assumes individual sample sizes are equal.) (Acceptable range 2 to 140,000).
Ending Sample Size. (For charts only) Final sample size for calculation of all Power vs. Sample Size charts. (Power vs. N chart assumes individual sample sizes are equal.) (Acceptable range 5 to 150,000).
Starting Standardized Effect. (For charts only) Initial standardized effect size for calculation of Power vs. Standardized Effect chart (acceptable range -10 to 9).
Ending Standardized Effect. (For charts only) Final standardized effect size for calculation of Power vs. Standardized Effect chart (acceptable range -9 to 10).
Starting Alpha Level. (For charts only) Initial alpha level for calculation of Power vs. Alpha Level chart (acceptable range 0.0001 to 0.2499).
Ending Alpha Level. (For charts only) Final alpha level for calculation of Power vs. Alpha Level chart (acceptable range 0.0002 to 0.25).