covariate


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covariate

(ˈkəʊˌvɛərɪɪt)
n
(Statistics) a statistical variable that changes in a predictable way and can be used to predict the outcome of a study
References in periodicals archive ?
The proposed method of analysis is based on a growing literature on design of covariate balanced randomized clinical trials (Pocock and Simon 1975; Wei 1978; Atkinson 1982; Signorini et al.
Spatial analysis with terrain attributes represented by numerical surface models as covariate to predict soil units were exemplified for McBratney et al.
We considered several approaches for urine dilution adjustment of arsenic concentrations: 1) no adjustment; 2) creatinine as an independent covariate in the regression model; 3) arsenic concentration divided by creatinine concentration ([micro]g/g); 4) covariate-adjusted standardization of arsenic concentration divided by creatinine concentration ([micro]g/g); 5) osmolality as an independent covariate in the regression model; 6) arsenic concentration divided by osmolality ([micro]g/mOsm/kg); 7) urinary flow rate as an independent covariate in the regression model; and 8) arsenic concentration multiplied by urinary flow rate to obtain excretion rate ([micro]g/hour).
We then used weighted model averaging based on model weights (w) calculated based on AICc to estimate the effect size and unconditional standard error of each covariate on occupancy (Burnham and Anderson, 2002; Doherty et al, 2012).
The final compartmental model included a categorical covariate to account for this lag in absorption as well as body weight as a covariate of total body clearance (relative to unknown bioavailability).
This allows analysis of covariate effects to be carried out using simple models at the smallest scale with negligible autocorrelation, maximising sample size while reducing model complexity.
The covariate analysis showed that lithology, road buffer, drainage density, and terrain units positively influenced the outcome of the model whereas land cover had a negative influence in the final model.
In cases where the covariate was associated significantly with the response variable, the relationship was assessed graphically on scatter plots with linear regression used to plot a trend line.
where P [sub]TVij is the typical individual value of the i [sup]th individual's j [sup]th PK parameter, P [sub]TVj is the typical group value of the j [sup]th PK parameter, and [INSIDE:2] are the i [sup]th individual's k [sup]th covariate and its mean, respectively.
We also used covariate data bearing on sampling variation to refine our estimate of population trend.