Impact Evaluation Glossary

Please send comments or suggestions on this glossary to [email protected]. Recommended citation: 3ie (2012) 3ie impact evaluation glossary. Attribution The extent to which the observed change in outcome is the result of the intervention, having allowed for all other factors which may also affect the outcome(s) of interest. Attrition Either the drop out of participants from the treatment group during the intervention, or failure to collect data from a unit in subsequent rounds of a panel data survey. Either form of attrition can result in biased impact estimates. Average treatment effect The average value of the impact on the beneficiary group (or treatment group). See also intention to treat and treatment of the treated. Baseline survey and baseline data A survey to collect data prior to the start of the intervention. Baseline data are necessary to conduct double difference analysis, and should be collected from both treatment and comparison groups. Beneficiary or beneficiaries Beneficiaries are the individuals, firms, facilities, villages or similar that are exposed to an intervention with beneficial intentions. Bias The extent to which the estimate of impact differs from the true value as result of problems in the evaluation or sample design (i.e. not due to sampling error).