[R-sig-ME] Sample size calculation

[Lenth, Russell V]

Yes, that was a typo. Just delete "nets" and you get what I meant. Sorry about that.

Russ

Sent from my iPad

> On Jan 1, 2014, at 10:16 AM, "Ben Bolker" <bbolker at gmail.com> wrote:
> 
>> On 14-01-01 09:21 AM, Lenth, Russell V wrote:
>> 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
> 
>  Seems like very good advice to me (although I'm not sure what
> "variance component nets" means -- is that a typo?)
> 
>  If you don't have pilot data but you know enough about your system to
> have some idea what realistic variance components and effect sizes
> should be (and if you don't, you probably don't know enough to design a
> sensible experiment in any case!)
> 
>  There are several packages dedicated to power analysis for mixed
> models (pamm, longpower, nlmeU, odprism), mostly (all?) by simulation.
> The simulation capabilities in the development version of lme4 make it
> easier to roll your own power analysis.
>> 
>>> 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
>> 
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