Variance components questions
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 ? ? ? ?[[alternative HTML version deleted]]
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