Stratification allows to control for confounding by creating two or more categories or subgroups in which the confounding variable either does not vary or does not vary very much. The Mantel-Haenszel formula is applied in cohort and in case-control studies to calculate an overall, unconfounded, effect estimate of a given exposure for a specific outcome by combining stratum-specific relative ris...

The current study research showed the nature and potential sources of gaps in mathematics achievement between English language learners (ELLs) non-English (non-ELLs). gap was examined using three DIF methodologies: including Mantel-Haenszel procedure, Rasch model, Hierarchical Generalized Linear Model (HGLM). These were conducted at item level contrast to total test level. Results revealed that...