0 votes
in Use of WebPower by jhk202105 (140 points)

Please let me illustrate my question with a concrete example of power analysis for the following model (some irrelevant parts have been omitted to save space):

library (WebPower)

model.2f <- '

F1 =~ a*x1 + start (.55)*x1 + start (.7)*x2 + start (.7)*x3

F2 =~ b*x4 + start (.6)*x4  + start (.6)*x5 + start (.5)*x6

F1 ~~ start (1)*F1

F2 ~~ start (1)*F2

F1 ~~ start (.3)*F2


x1 ~~ start(.6)*x1


power.2f <- wp.mc.sem.basic(model = model.2f, indirect = NULL, nobs = 100, nrep = 5000)

summary (power.2f)


In the outputs, the power analysis results (MSE, SD, Power, Coverage) for the indicator variables, x1 and x4, of the two respective factors in the model are not available, though I have set both factors’ variances as 1 and the loadings of x1 and x4 as freely estimated.  By “not available” I mean their corresponding output rows are like:

                       True  Estimate      MSE      SD     Power Coverage

  F1 =~    x1        (a)      0.550    0.550    0.000    0.000      NaN    0.000


  F2 =~    x4        (b)      0.600    0.600    0.000    0.000      NaN    0.000

Grateful if you could advise how the power analysis results can be displayed for ALL the indicator variables (x1 – x6 in this case) of a measurement model when the latent variables they indicate have been set to have unit variances.

1 Answer

0 votes
by johnny (3.3k points)

You can try adding std.lv = T in the function so that

power.2f <- wp.mc.sem.basic(model = model.2f, indirect = NULL, nobs = 100, nrep = 5000, std.lv=T)