Intervention Follow-Up, Outcome Evidence and Confounding
An intervention is not successful because it was completed. Follow-up compares comparable pre/post evidence, expected response timing, new spread, incidence, severity and relevant confounders. Where evidence is incomplete, the correct conclusion may be unresolved rather than success or failure.
Learning objectives
- LO-LH-TECH2-004-02
- LO-LH-TECH2-004-03
- LO-LH-TECH2-004-05
Key vocabulary
Pre-intervention observation set used for a defensible comparison.
A changing factor that can distort attribution of an observed outcome to the intervention.
Defined evidence used to judge whether the intended response occurred.
Define what improvement would look like
Before evaluating response, identify the intended measurable outcome: reduced new detections, lower incidence, lower severity, reduced trap counts, constrained spread, or another authorized program metric.
Use repeated comparable rounds
One clean leaf or one low trap is not control evidence when the multi-round trend disagrees. Evaluate enough comparable locations and rounds to support the scope of the conclusion.
Document confounding instead of forcing attribution
Sanitation changes, environmental corrections, crop removal, altered sampling effort or overlapping controls can affect the apparent outcome. Record them and limit causal language to what the evidence supports.
Worked examples
- Trap counts fall 60%, but half the traps were removed; the apparent improvement cannot be interpreted without correcting for sampling effort.
- Incidence falls after an authorized biological release, while affected crop is also removed and humidity is corrected; report improvement but do not attribute the whole effect to one intervention without evidence.
Common mistakes
- Calling control success from one observation.
- Ignoring simultaneous environmental or sanitation changes.
- Moving the follow-up date until the numbers look better.
Practical application
For an intervention record, define baseline, expected outcome, follow-up schedule, comparable measures, confounders and the criteria for continue/hold/escalate review.
Lesson summary
Treatment follow-up measures outcomes against a comparable baseline and makes uncertainty visible.