A familiar summary score may depend on how questionnaire items are grouped.
What the source reports
The retrospective methods study reanalyzed sixteen Norris visual-analogue items from male volunteers exposed to benzodiazepines, THC or scopolamine. Consensus clustering did not support stable conventional three-cluster grouping across these datasets; a two-cluster approach performed better under the examined assumptions.
Limits and uncertainty
The result depended on the available samples and drugs. The analysis did not quantify every individual’s variation and lacked female participant data. Statistical clustering is not proof that two underlying biological states explain all sedation or mood effects.
Application to expert review
For interpreting a published drug-effect score, identify its component items and scoring model. Do not equate a change in a grouped subjective rating with objective driving impairment or a specific memory deficit. Measurement structure is part of the evidence, not merely a presentation choice.
Source and related reading
Source: Publication PMC8084085. Applications to expert review are interpretive analysis.
Related reading: Hysteroscopy Meta-Analysis Claimed a Nausea Benefit That Its Interval Did Not Establish.