Power Calculation, Two Proportions, Z-Test

Power calculation for comparing two proportions via Z-Test with option for charts of power vs. sample size (assuming equal sample sizes), sample 1 size, sample 2 size, population one proportion value, 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).
Pi1 Population number one proportion (acceptable range 0.0001 < Pi1 < 0.9999).
Pi2 Population number two proportion (acceptable range 0.0001 < Pi2 < 0.999).
Alpha Level Alpha level (Type I error rate for Z-statistic) (acceptable range 0.0001 to 0.25).
Hypothesis type Hypothesis type selection:

 Two-tailed (Pi1=Pi2, population one proportion = population two proportion);

 One-tailed (Pi1<=Pi2, population one proportion <= population two proportion);

 One-tailed (Pi1>=Pi2, population one proportion >= population two proportion) .
Applies Continuity Correction Type of calculation selection:

 If TRUE, apply the continuity correction.
Employ Equal N Type of calculation selection:

 If TRUE, limit group 1 and group 2 to the same sample size (Sample size specified for Sample One Size will apply to both N1 and N2);

 If FALSE, N1 and N2 can be varied independently for the analysis.
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. Population One Proportion, 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 Proportion (Pi1). (For charts only) Initial population one proportion value for calculation of Power vs. Population One Proportion chart (acceptable range 0.0001 to 0.9999).
Ending Proportion (Pi1). (For charts only) Final population one proportion value for calculation of Power vs. Population One Proportion chart (acceptable range 0.0002 to 1.0).
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) Ending Alpha Level. (For charts only). Final alpha level for calculation of Power vs. Alpha Level chart (acceptable range 0.0002 to 0.25).