Blinding
Definition
Withholding treatment allocation from participants, investigators or outcome assessors. It fails in practice whenever a compound has obvious effects, which is a known weakness of trials in this area.
What this means for research sourcing
Understanding evidence quality helps researchers prioritize compounds. Volta's research library summarizes the literature behind stocked compounds.
Related Terms in Evidence & Research
Double-Blind
Neither participants nor investigators know who is in which arm, so expectation cannot colour reported symptoms or outcome assessment. It is a design feature, not a guarantee, and papers increasingly report whether blinding held.
Open-Label
Everybody knows who is receiving what. Open-label extensions following a blinded trial give useful long-term safety data, and their efficacy figures are not placebo-controlled and should not be read as though they were.
Placebo
An inactive preparation made to look like the active one, given to the comparison arm. Placebo groups routinely improve, which is exactly why an uncontrolled result cannot be read as evidence of an effect.
Placebo-Controlled
A design in which the comparison arm receives placebo rather than nothing or another active agent, isolating the intervention's own contribution to whatever changed.
Placebo Effect
Improvement that follows the expectation of treatment rather than the treatment itself. It is real, measurable and occasionally large, and separating it from a drug effect is the entire purpose of a control arm.
Crossover Trial
A design in which each participant receives both treatments in sequence with a washout between, so each person acts as their own control. It needs fewer participants and only suits stable, reversible conditions.
Intention-to-Treat
Analysing every participant in the arm they were randomised to, whether or not they finished. It preserves the randomisation and usually gives a more conservative answer than analysing completers only.
Endpoint
A defined, measurable outcome a trial uses to judge an intervention. Which endpoints were chosen, and when, is as informative as the results reported against them.