Measurement and evaluation
Before-and-after study
Étude avant-après
Before-and-after study is an evaluation comparing conditions before and after an intervention using a stated method. Curb studies should account for seasonality, unrelated street changes, observation coverage, and comparison locations where possible, since a change following an intervention does not by itself establish that the intervention caused it.
Understanding the term
Choose outcomes and observation periods before interpreting results. Document implementation changes so that the evaluated intervention matches what actually operated rather than the original plan alone.
Every reported measure needs a geographic boundary, observation period, unit, and documented calculation method. State how missing data, temporary closures, and sessions crossing the observation boundary are treated. Use distributions or separate user categories where an average hides important differences. Compare consistent definitions across sites and periods, and distinguish an observed association from a demonstrated causal effect. The appropriate indicator follows the policy question rather than whichever field a monitoring system happens to provide.