Strata Versus Cohort: A Clarification

IRT Essentials

We’ve seen confusion in recent IRT (IVR/IWR) RFPs and study protocols in the use of ‘strata’ and ‘cohort’ when describing desired approaches to randomization. The words are often used in opposition – that is, one is often specified when it’s really the other that’s required.
This confusion in terminology can negatively impact the bidding timeframe, requiring back and forth clarification between vendor and sponsor, or worse yet, can wrongly inflate or deflate the final bid tally. Correcting after the fact also takes additional time. Better by far to specify the strata or cohort requirements correctly from the outset