Brownstein, N.C., Cai, J. Tests of trend between disease outcomes and ordinal covariates discretized from underlying continuous variables: simulation studies and applications to NHANES 2007<U+FFFD>2008. BMC Med Res Methodol 19, 2 (2019). 10.1186/s12874-018-0630-7. Available in html format or pdf format.
- Ordinal covariates require special attention. The coefficients associated with these covariates are expected to follow an increasing or descreasing trend. This paper shows how to test for such a trend when there is an underlying continuous variable used to created the ordinal covariate.