[R-sig-ME] Sample size calculation

[Lenth, Russell V]

Maybe I can help. But what's the situation? Do you already have pilot data analyzed with one of those packages? If so, you can use that analysis to estimate the variance component nets needed for the sample-size calculation. If not, your first step really is to do such a pilot study. 

The next step is to figure out the power function for the test(s) of interest. That depends on the intended model for the data and the expected mean squares (at least under the usual uniformly wonderful normality conditions). You also need to establish what size difference or other effect is of interest to detect with a stated power and significance level. 

There is software that can help with the power calculations, but let's get more details first on those other steps.

Russ Lenth

Sent from my iPad

> Hi list
> Can someone illustrate me how is  possible  to calculate  sample size for linear mixed model (not repeated measure) build with  lme4 or nlme package
> Thank in advance
> happy Holidays 
> Bonitta Gianluca