Accumulation Bias in Meta-Analysis: The Need to Consider Time in Error Control

Understand

Studies accumulate over time and meta-analyses are mainly retrospective.

• These two characteristics introduce dependencies between the analysis time, at which a series of studies is up for meta-analysis, and results within the series.
• Dependencies introduce bias --- Accumulation Bias --- and invalidate the sampling distribution assumed for p-value tests, thus inflating type-I errors.
• But dependencies are also inevitable, since for science to accumulate efficiently, new research needs to be informed by past results.