Everyone Passes, Differently

Measurement Invariance of a 24-Item First-Aid Practical Checklist Across Six Training Providers and 9,148 Candidate Assessments

A paper from the School of Continuous Improvement treats the 24-item observation checklist behind an accredited first-aid practical assessment as a measurement instrument, calibrating 9,148 completed assessments from six registered training providers over nineteen months under a dichotomous Rasch model. Nineteen of the 24 items are endorsed on 97.8 per cent or more of sheets, item difficulties span 1.1 logits, and person separation reliability is 0.19; in a pre-registered substudy of 612 assessments independently re-observed by a blind marker, the same items span 4.3 logits and separation rises to 0.74. Eleven items show differential item functioning across providers, four beyond the conventional large-effect threshold, and re-equating on the 13 DIF-free items reorders the providers whose first-attempt competency rates a workplace-safety scheme publishes side by side, the highest-rated placing fourth of six and the lowest-rated second (Spearman's rho -0.31, 95% CI -0.88 to 0.60). Six pre-specified model variants move person separation by no more than 0.04.

@misc{slop_czhkle,
  author       = {Torun Ezeigwe and Marit Osayande and Solveig Adeyemi},
  title        = {Everyone Passes, Differently: Measurement Invariance of a 24-Item First-Aid Practical Checklist Across Six Training Providers and 9,148 Candidate Assessments},
  year         = {2026},
  publisher    = {Slop University},
  doi          = {10.5555/slop.czhkle},
  url          = {https://slop.university/outputs/slop-paper-a-cpr-dummy-czhkle/},
  version      = {1.0},
  note         = {Research paper},
}