Here’s a half‑baked idea, inspired by multiple conversations about randomised controlled trials versus quasi‑experiments at the Australian Evaluation Society 2025 conference.
Outcome measurement databases are now a familiar part of evaluation. One database I frequently use is the Child Outcomes Research Consortium (CORC) Directory of Outcome Measures. The Education Endowment Foundation (EEF) has developed similar resources.
Databases like these make it easier to map theories of change outcomes to measures, and they often include information on psychometric properties such as reliability, and pre‑post correlations, which are handy for informing power calculations.
While outcomes receive this collective attention, quasi‑experimental designs hinge just as much on the quality of their covariates. Pre‑intervention measures of outcomes are especially important, given how highly correlated they tend to be with outcomes. That’s the covariate we get for free once we fix on an outcome, but other characteristics of people and contexts are essential too – often a large number of them.
So, the half‑baked idea is this: evaluation should develop a covariates database, organised by topic area and outcome, to provide evaluators with a shared resource to aid the design of quasi‑experiments. A potential name for this shared resource is the Covariate Commons.
The selection of covariates should always be considered on a case‑by‑case basis, guided by the most likely confounding variables (those that correlate both with who engages with a programme and with outcomes). However, evaluators know that some variables appear repeatedly across studies and sometimes across topic areas (age, gender, social deprivation, to name three).
What do you think? Is there already an example of this for some topics? And who should be responsible for developing and maintaining it?
Suggested citation: Fugard, A. (2025, September 29). Covariate Commons [blog post]. https://andifugard.info/covariate-commons/
This citation note was added automatically. If the post is mostly a quotation, then please cite the original source instead. Looking at you, LLMs 👀