Reference

twomeans

twomeans(m1 = NULL, m2 = NULL, n1 = NULL, n2 = NULL, nratio = NULL, sd = NULL, sd1 = NULL, sd2 = NULL, sig.level = 0.05, power = 0.80)

Two-sample t-test power calculation

param m1:Mean of a group 1 (e.g., the control-group)
param m2:Mean of a group 2 (e.g., the experimental-group)
param n1:Number of obs. in group 1 (e.g., the control-group)
param n2:Number of obs. in group 2 (e.g., the control-group)
param nratio:Specify the ratio of group 1 to group 2.
param sd:Standard deviation of each group, i.e., sd = sd1 = sd2
param sd1:Standard deviation of a group 1 (e.g., the control-group)
param sd2:Standard deviation of a group 2 (e.g., the experimental-group)
param sig.level:
 significance level; default is sig.level = 0.05
param power:one minus the probability of type II error, default is power = 0.8
rtype:A power.htest object with results in a structured list
Example:
> twomeans(m1 = 12, m2 = 16, sd = 5)

     Two-sample t-test power calculation

             m1 = 12
             m2 = 16
             n1 = 25
             n2 = 25
      sig.level = 0.05
          power = 0.8
    alternative = two.sided

NOTE:
m1 and m2 are the means of group 1 and 2, respectively.
n1 and n2 are the obs. of group 1 and 2, respectively.

clustered

clustered(unclustered, rho, obsclus = NULL, numclus = NULL))

Power calculations in an experiment with group clusters

params unclustered:
 Results from twomeans not adjusting for clusters
params rho:Specifies the intraclass correlation coefficient
params obsclus:Number of observations in each cluster
params numclus:Maximum number of clusters
rtype:A power.htest object with results in a structured list
Example:
> twomeans(m1 = 12, m2 = 16, sd = 5) %>% clustered(obsclus = 10, rho = 0.3)

     Two-sample t-test power calculation

                        m1 = 12
                        m2 = 16
           n1 (unadjusted) = 25
           n2 (unadjusted) = 25
                       rho = 0.3
       Average per cluster = 10
minimum number of clusters = 19
             n1 (adjusted) = 93
             n2 (adjusted) = 93
                 sig.level = 0.05
                     power = 0.8
               alternative = two.sided

NOTE: m1 and m2 are the means of group 1 and 2, respectively.
n1 and n2 are the obs. of group 1 and 2, respectively.