The Psychometrician’s Handbook / Interactive / Correlations / Restricted range

Interactive · from Volume 1

Restricted range

One sample, one relationship. Narrow the band you recruit from and the correlation collapses, without a single data point changing.

Full sample--
Inside the band--
Patients in band--

Drag the dashed edges to resize the band, or grab the middle and slide the whole thing along. The sliders do the same job.

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Keep going

Sample size and stabilityAt n = 25 the estimate swings. At n = 200 it settles.Measurement error and attenuationAdd noise to either measure, watch r pull toward zero.