[R-sig-ME] Variance components questions

[Clifford Long]

Karim,

You might find this reference useful for the statistical model (but
not the R code).

"Design and Analysis of Gauge R&R Studies:  Making Decisions with
Confidence Intervals in Random and Mixed ANOVA Models" by Burdick,
Borror, Montgomery.
ISBN 0-89871-588-1

It discusses Measurement System Analysis (of which Gauge
Reproducibility and Repeatability are a subset), and the role of
Variance Components based on Random Effects models.  It also gives
information on the calculation of confidence intervals.

HTH

Cliff




On Mon, Feb 21, 2011 at 5:00 PM, Karim Lounes <kclounes at gmail.com> wrote:
> Hi All,
> I am a biochemist with limited background in statistics, so please forgive
> the naivety of my question.
> I am interested in estimating the precision of a measurement system and the
> variance components of three factors.
> This is how the experiment was designed: 5 samples, each considered a level
> were measured. Each sample was measured twice a day (run) for 10 days (days)
> by two different operators (operator). Each measurement was replicated 3
> times. The factor (days) is not continuous as the goal was to generalize the
> estimation of the precision of the measurement system for all days.
> I have read a number of posts on this list and also read Mr. bates online
> book of lem4.
> >From what I understood the model would be a crossed design and I  run the
> following analysis:
>
> Measurement ~ samples + (1|days) +  (1|run) +(1|operator)
>
> Is this model appropriate? and is there a way to gauge the precision of the
> the estimates of the variance components by a confidence interval?
>
> Thank you for your help
>
> Regards
>
> Karim
>
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>
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