| name | epsl-data-analysis |
| description | Use when reducing and reporting data for an Earth and Planetary Science Letters (EPSL) manuscript — full analytical-uncertainty budgets for isotope and geochronology data, defensible statistics (MSWD, weighted means, Bayesian age models), and inversion/model diagnostics. It guides reduction and reporting norms; it does not fabricate results. |
Data Analysis (epsl-data-analysis)
EPSL's methods-transparency culture is strictest exactly where the journal is strongest: isotope
geochemistry and geochronology. Reviewers expect every headline number to arrive with its complete
error budget — internal precision, external reproducibility, standard and blank corrections, and
systematic terms like decay-constant uncertainty — and they expect model results to arrive with their
resolution limits. Design choices live in epsl-study-design; deposition and supplements in
epsl-reporting-and-reproducibility.
When to trigger
- Reducing isotope, geochronologic, elemental, or geophysical data to reportable results
- Deciding which uncertainty terms to propagate and how to quote them
- Computing weighted means, isochrons, concordia intercepts, or Bayesian age–depth models
- A reviewer asked for the error budget, the MSWD, or a resolution test
Reporting norms EPSL expects
- State the full uncertainty ladder. Quote internal (within-run) precision, external
reproducibility from repeat standards/replicates, and — when comparing across methods or to other
studies — systematic terms (decay constants, tracer calibration, spectrometer bias). Say which
ladder rung each quoted ±X σ includes, and whether σ means 1σ, 2σ, or 95% CI.
- Anchor to community values. Name the reference materials with the values used, the
normalization scheme (e.g., what δ is measured against), and the decay constants adopted, with
citations — so the numbers remain comparable when calibrations shift.
- Statistics that match geochemical data. Weighted means with MSWD reported and interpreted
(MSWD ≫ 1 means scatter beyond analytical error — say why); isochrons with the regression model
named; mixtures and outliers handled by a stated rule, not silent deletion.
- Age models with honest priors. Bayesian age–depth or eruption-tempo models report priors,
convergence, and sensitivity to them; deposit the model input/config.
- Inversions come with diagnostics. Resolution/recovery tests, misfit and trade-off curves, and
an explicit statement of what the data cannot see; never present a smoothed model as if it were data.
- Blanks and detection. Report total procedural blanks and their variability; state how
blank-sensitive results (small samples, young ages, low abundances) respond to the blank range.
Uncertainty-reporting table reviewers work down
| Element | What to report | If omitted, the reviewer assumes |
|---|
| σ-level and type | 1σ/2σ/95% CI; internal vs external | numbers are not comparable |
| Reference materials | measured vs accepted values, per session | accuracy unverified |
| Blanks | magnitude + variability + correction | small samples untrustworthy |
| Decay constants / tracer | which values, cited | ages not portable across studies |
| MSWD / goodness of fit | value + interpretation | scatter hidden in the mean |
| Model resolution | recovery tests, trade-offs | structure may be artifact |
Worked micro-example (illustrative — a weighted-mean age that survives review)
Twelve single-zircon U-Pb analyses from one ash bed (illustrative numbers):
- Ten young analyses give a weighted mean of 66.021 ± 0.024 Ma (2σ, analytical only), MSWD = 1.3 —
scatter consistent with analytical error, so a single population is defensible.
- Two older grains are excluded as inherited by a pre-stated criterion (resolvably older than the
main cluster), and shown in the figure anyway.
- Reported as: "66.021 ± 0.024/0.031/0.075 Ma (2σ: analytical / +tracer / +decay constants), MSWD 1.3,
n = 10/12" — the three-tier bracket lets a reader compare against Ar-Ar or astrochronologic ages
without emailing the authors.
The habit that prevents most queries: every mean is accompanied by its MSWD, its n-of-N, and a plot
showing the excluded analyses.
Referee-pushback patterns and the venue-specific fix
- "Uncertainties are quoted but not defined." → State σ-level, and split analytical vs systematic
terms wherever the result is compared to external ages or data.
- "MSWD indicates overdispersion." → Do not just widen errors; identify the geological or analytical
source of scatter and let the interpretation absorb it.
- "The anomaly is at the edge of resolution." → Show the recovery test at that node; soften or drop
claims the test cannot support.
Anti-patterns
- A headline age or rate with a bare ± and no statement of what it includes
- Standards measured but never reported against accepted values
- Outlier analyses removed without a stated rule or a visible plot
- MSWD omitted, or quoted without interpretation
- Tomographic/model features discussed where resolution tests show smearing
- Comparing your ages to literature ages without harmonizing decay constants
Output format
【Headline number】value ± (σ-level; analytical/+systematic) + units + n
【Traceability】standards vs accepted values; blanks; constants cited
【Statistics】weighted mean/isochron/Bayesian model + MSWD/diagnostics
【Exclusions】rule stated + shown in figures? [Y/N]
【Model diagnostics】resolution/sensitivity reported? [Y/N or N/A]
【Next】epsl-figures-and-tables
Supplementary resources
