The P.E. (median deviation) serves as an equal-step unit of difficulty, defined as the distance cutting off 25% of measures next the median¶

Claim · All claims
Evidence · 1 study · design r2 · q2
Currency · newest study 1919 · not yet checked against its sources · not reviewed by a person

Subclaims¶

q2 i? One P.E. is the distance from the median whose ordinate cuts off 25% of the measures between itself and the median, and P.E. distances are comparable across groups when group variabilities are approximately equal. → Herring 1919

Evidence¶

Herring 1919¶

Herring, J. P. (1919). Derivation of a scale to measure abilities in scientific thinking. The Journal of Educational Psychology. https://psycnet.apa.org/journal/edu

q2 · i? · design · r2

Definitional statement in the section on the probability curve: the P.E. represents equal steps of difficulty within a group, with the median as the zero reference point and 50% of cases between -1 and +1 P.E. No effect size is printed.

"The P. E. of a normal group of unselected measures is that distance below or above the median of its surface of distribution whose ordinate cuts off just 25% of the measures between itself and the median."

Discussion¶

Related Claims¶

• Intermedian grade distances on the scientific-thinking scale are derived from the per cent of each grade's pupils lying between successive grade medians — related
• Question E was answered by all 27 high-school pupils, establishing a zero-difficulty reference 2.191 units below the median — related
• The zero point of the scale is located from the zero-scoring pupils, giving a weighted average distance O-MIII of 1.654 P.E. — a narrower finding that bears on this claim