Geometric summary specification
Method review date: 2026-11-03

Instructions: Save a copy, complete blanks and record unresolved questions. Use fictional or aggregate values only; never patient identifiers. This planning aid does not certify an analysis.

ESTABLISH MEASUREMENT MEANING
Variable and unit: ____
Population/timepoint: ____
Why a multiplicative/log-scale summary fits the question: ____
Zero, negative, below-detection and missing values present? ____
Prespecified handling and scientific rationale: ____ (do not add an arbitrary constant)

USE A FICTIONAL REFERENCE
Fictional positive values: ____
Natural logarithms: ____
Number n: ____
Mean log=sum(log values)/n: ____
Sample SD log=sqrt(sum((log−mean log)²)/(n−1)): ____
Geometric mean=exp(mean log): ____
Geometric SD factor=exp(sample SD log): ____

REVIEW INTERPRETATION
Geometric mean retains the original measurement units; geometric SD is a multiplicative dimensionless factor.
Neither is automatically a confidence interval.
Distribution plots/lognormal assumptions assessed separately: ____
Do not assume geometric mean equals the sample median.

FREEZE REPORTING CONVENTION
Software/function/version/options: ____
Independent recomputation and rounding: ____
Observed/missing counts, units and convention in table footnote: ____
Sensitivity analyses needed for excluded/nonpositive values: ____

Practical guide: https://www.statmedanalysis.com/blog/geometric-mean-log-scale
Project/version: ____  Completed by role/date: ____