Nested data on lab testing of eggs
Consistency between laboratory tests is important and yet the results may depend on who did the test and where the test was performed. In an experiment to test levels of consistency, a large jar of dried egg powder was divided up into a number of samples. Because the powder was homogenized, the fat content of the samples is the same, but this fact is withheld from the laboratories. Four samples were sent to each of six laboratories. Two of the samples were labeled as G and two as H, although in fact they were identical. The laboratories were instructed to give two samples to two different technicians. The technicians were then instructed to divide their samples into two parts and measure the fat content of each. So each laboratory reported eight measures, each technician four measures, that is, two replicated measures on each of two samples.
data(eggs)
A data frame with 48 observations on the following 4 variables.
Fata numeric vector
Laba factor with levels I II III IV V VI
Techniciana factor with levels one two
Samplea factor with levels G H
Bliss, C. I. (1967). Statistics in Biology. New York: McGraw Hill.
data(eggs) ## maybe str(eggs) ; plot(eggs) ...
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