"fixed variables" is correct and usable in written English.
You can use it to refer to particular values or factors that remain unchanged in a situation. For example, "We had to work around the fixed variables of our budget in order to accomplish our goal."
The final model was rerun on the full data set, entering first fixed variables and then modifiable ones to provide data on how much variability was explained by each.
We treated the individual respondent as a random variable and service metric and demographic factors as fixed variables.
In the setup of Eq. (3), any effect that may originate due to the influence of fixed variables is controlled by the fixed effects model (Verbeek 2004).
See Appendix C. As a consequence of the discussion above, we can replace the SRPC problem (15) by two simple subproblems, coupled to each other via fixed variables (power and network variables).
Comorbidity, socioeconomics, and concomitant medication were included as fixed variables obtained at baseline.
Genotype, flat, and position within the flat (corner, edge, or interior) were treated as fixed variables.
Treatment, year and their interaction were included as fixed variables, while tree identity and its interaction with treatment as random effects.
A mixed linear multivariate model was applied to the prospective study sample results, with gestational age and presence of peripheral parasites as fixed variables, and study participant as a random variable.
This model used: (i) the number of adult secondary colonizers that emerged from branches as the response variable, (ii) treatment, year and their interaction as fixed variables, and (iii) plant identity and its interaction with treatment as random effects.
Using an ANOVA model with untransformed data (the means for each pot), with continent and treatment as fixed variables and site as a random variable, only the effect of -catechin treatment was significant for emergence (F = 64.12; df = 1,54; P = 0.004) and for height (F = 32.55; df = 1,40; P = 0.0011).
Concomitant pharmacotherapy was used as fixed variables in both types of analyses performed.
