TABLE 4

Covariates used in the study

CovariateEncodingDescriptionSummary
AgeIntegerAge in daysMean = 61, SD = 4, 31–85
ApparatusCategoricalExperimental unit usedGroups = 4, size = 348–526
CageCategoricalCage in which animal was housedGroups = 435–549, size = 1–7
Cage densityIntegerNo. of animals in a cageMean = 4.7, SD = 1.1, 2–7
ExperimenterCategoricalWho performed the testGroups = 2–12, size = 7–457
FamilyCategoricalSibship of animalGroups = 160–180, size = 1–52
HourCategoricalHour of the day test was performedGroups = 1–11, size = 1–2307
LitterIntegerNo. litter the animal came fromMean = 2.2, SD = 1.3, 1–8
MonthCategoricalMonth test was performedGroups = 12, size = 32–314
SeasonCategoricalSeason test was performedGroups = 4, size = 284–788
SexCategoricalSex of the animalGroups = 2, size = 806–1293
Study dayIntegerDay into study that test was performed (day 1 is Jan. 20, 2003)Mean = 306, SD = 160, 1–621
Test orderIntegerOrder in which animal was tested that dayMean = 2.8, SD = 1.4, 1–7
WeightReal no.Body weight (g) at 9 wkMean = 23.9, SD = 4.2, 12–39.1
YearCategoricalYear of testGroups = 2, size = 711–1517
• “Encoding” refers to how a covariate was modeled statistically. For numerical covariates, the column headed “Summary” gives the grand mean and standard deviation over all phenotypes, followed by the minimum and maximum values observed for any given phenotype. For categorical covariates Summary gives the number and size of categories seen for a typical phenotype. For example, for phenotypes in which the experimenter covariate was present, there were between 2 and 12 experimenters who each recorded data for between 7 and 457 mice.