AB_t2n {pwrAB}

Two-Sample t-Test Power Analysis

Description

AB_t2n performs the power analysis for AB testing. It uses the Welch's t-test, which allows for the standard deviation to vary across groups.

Usage

AB_t2n(N = NULL, percent_B = NULL, mean_diff = NULL, sd_A, sd_B,
  sig_level = NULL, power = NULL, alternative = c("two_sided", "less",
  "greater"), max_sample = 1e+07)

Arguments

N

Total number of observations (sum of observations for groups A and B)

percent_B

Percentage of total observations allocated to group B (between 0 and 1 - e.g. input .5 for 50%)

mean_diff

Difference in means of the two groups, with mean_B - mean_A

sd_A

Standard deviation of group A

sd_B

Standard deviation of group B

sig_level

Significance level (Type I error probability)

power

Power of test (1 minus Type II error probability)

alternative

Character string specifying the alternative hypothesis, must be one of "two_sided" (default), "greater" or "less"

max_sample

Maximum sample size that is searched for

Details

Exactly one of the parameters 'N', 'percent_B', 'mean_diff', 'sig_level', and 'power' must be passed as NULL, and the omitted parameter is determined from the others. sd_A and sd_B must be specified. When 'percent_B' is the parameter omitted, two solutions may exist, in which case the smaller value will be returned

Value

Object of class "power.htest", a list of the arguments (including the computed one).

Examples

# Search for power given other parameters
AB_t2n(N = 3000, percent_B = .3, mean_diff = .15, sd_A = 1,
sd_B = 2, sig_level = .05, alternative = 'two_sided')

# Search for sample size required to satisfy other parameters
AB_t2n(percent_B = .3, mean_diff = .15, sd_A = 1,
sd_B = 2, sig_level = .05, power = .8, alternative = 'two_sided')