Placebo Effect
Definition
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.
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
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.
Primary Endpoint
The single outcome a trial was designed and powered to answer, fixed before data collection. Secondary endpoints are informative and are not what the trial succeeded or failed on, a distinction that press releases regularly blur.
Biomarker
A measurable indicator standing in for a process, a disease state or a response. Serum IGF-1 is the usual biomarker in growth hormone secretagogue work, and a biomarker moving is not the same as an outcome improving.
HbA1c (Glycated Hemoglobin)
A blood measure reflecting average glucose over roughly the preceding two to three months, reported as a percentage. It is the standard primary endpoint in metabolic trials, which is why a result quoted in points of HbA1c appears in almost every incretin paper.
Effect Size
How large the difference an intervention produced actually was, in real units or as a standardised measure. Once significance is established this is the only question left that matters.
Statistical Significance
A judgement that a result is unlikely to have arisen by chance under the null hypothesis, conventionally at p below 0.05. It says nothing whatever about whether the difference is big enough to care about.
