Interactive · from Volume 1

Floor and ceiling effects

Scales have ends. A patient can get worse than the instrument is able to record, and everyone past that point is written down as the same score. Move the ceiling and watch how many patients the PRO stops being able to tell apart.

PRO vs clinician--

True severity vs clinician--

At a boundary--

The dashed floor and ceiling lines can be dragged directly, or use the sliders.

Floor of the PRO

Ceiling of the PRO

Keep going

Anscombe's quartetFour datasets, one correlation. r = 0.82 every time.Pearson vs SpearmanDrag a point. Watch the two coefficients disagree.