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decisionfacets

Would this candidate have passed with a different set of raters?

Decision accuracy and consistency for rater-mediated exams (oral exams, OSCEs, essay and constructed-response scoring), built on the many-facet Rasch rating scale model.

library(decisionfacets)

sim <- df_simulate(n_persons = 1000, n_items = 4, n_raters = 12,
                   raters_per_person = 2, severity_sd = 0.6, seed = 1)
fit <- df_fit(sim$data)                      # TAM if installed, else built-in JMLE

cut <- df_cut(16, decision_rule = "raw_total")
cf  <- df_counterfactual(fit, cut)           # per-candidate pass probabilities
cf                                           # most rater-dependent candidates first
df_attribute(cf)                             # measurement error vs rater assignment

Installation

From CRAN (once released):

install.packages("decisionfacets")

Development version from GitHub:

install.packages("pak")
pak::pak("edidatasolutions/decisionfacets")

The decision rule is the point

How much rater severity harms a candidate depends on what the board decides on:

`decision_rule`	severity reaches the decision?
`raw_total`	yes, directly
`fair_average`, `measure`	no; only through measurement precision

Internally every rule reduces to a raw-total cut that depends on the panel (harsher panels get lower cuts under measure-based rules), so pass probabilities are computed exactly by convolving category probabilities.

What each candidate gets

df_counterfactual() returns pass probabilities under the observed panel, an average-severity panel, and a random panel from the pool (enumerated when feasible), plus the best and worst panel. advantage is how far the assigned panel pushed the candidate toward the outcome they received; candidates with advantage >= 0.2 are flagged lenient_panel_pass or harsh_panel_fail.

df_attribute() splits expected misclassifications into measurement error (present even with average raters), rater assignment (observed minus average), and the expected cost of the random assignment design.

Validation (known truth, `inst/validation/mvp_recovery.R`)

1,000 candidates, 4 items, 12 raters (severity SD 0.6), 2 raters per candidate, cut = mean rating of 2:

Raw totals: 147 truly rater-dependent candidates. TAM flags 140, recovering 75% of true flags (79% of TAM’s flags are real). An oracle with the true parameters recovers 76%, so the remaining gap is measurement error from 8 ratings per candidate, not estimation error.
Expected misclassifications per 1,000: 156 under raw totals (114 measurement, 42 rater assignment) versus 116 under the measure rule (assignment about 2). TAM estimates: 157 / 119 / 39. Realized errors in the simulation: 147.

Status

layer	functions	status
data / model	`df_data`, `df_fit` (TAM, JMLE), `df_rater_effects`	done
decision	`df_cut`, `df_classify`	done
flagship	`df_counterfactual`, `df_attribute` (severity)	done
forward-looking	`df_simulate` done; `df_design`, `df_evaluate_design`	stubs
monitoring / output	`df_drift`, `df_report`	stubs

Current design limits: every panel rater scores every item for a candidate, panel sizes are equal, no missing ratings, severity only (no halo/drift terms). With few ratings per person, JMLE stretches the logit scale (~16% in the tests); prefer TAM.