Graduating the scale by compositing the ten test-score distributions yielded an approximately normal ability distribution, and the age norms for ages 10 to 14 fell in almost a perfectly straight line¶

Claim · All claims
Evidence · 1 study (2 entries) · associational r2 · q2
Currency · newest study 1918 · not yet checked against its sources · not reviewed by a person

Subclaims¶

q2 i? The median point values read off the composited distributions indicate that the distribution of abilities of the 121 pupils was approximately normal. → Otis 1918 q2 i? The age norms for ages 10 to 14 lay in almost a perfectly straight line, suggesting the norms are fairly reliable for the school population tested; the yearly increment of points below age 14 was approximately 40.5, and a line through the norms reached zero age at zero of the point scale. → Otis 1918 (2)

Evidence¶

Otis 1918¶

Otis, A. S. (1918). An absolute point scale for the group measurements of intelligence. Part I. The Journal of Educational Psychology, 9(5), 239-261. https://books.google.com/books/about/the_journal_of_educational_psychology.html

q2 · i? · design · r2

A graphical graduation procedure in which preliminary point values were assigned to scores by rank (the 30th individual given 40 points, the 90th given 60) and median point values across the ten test distributions were read at selected rank positions; the printed result is that the values "indicate that the distribution of abilities of the 121 pupils approximately normal".

"It should be stated that these values indicate that the distribution of abilities of the 121 pupils approximately normal."

Otis 1918 (2)¶

Otis, A. S. (1918). An absolute point scale for the group measurements of intelligence. Part I. The Journal of Educational Psychology, 9(5), 239-261. https://books.google.com/books/about/the_journal_of_educational_psychology.html

q2 · i? · associational · r2

Age norms were found by averaging total point scores of pupils within overlapping age windows and plotted in Fig. 2. The author reports that, unexpectedly, "the points representing the norms for ages 10 to 14 lay in almost a perfectly straight line", despite the omission of the fifth and seventh grades from the group tested.

"To our surprise, the points representing the norms for ages 10 to 14 lay in almost a perfectly straight line, which suggests that they are fairly reliable, at least, for the school population tested."

Discussion¶

Related Claims¶

• Ability distributions in grade-school children are non-normal, with ability clustering in the extreme ranks rather than the median — reports the opposite
• Galton's ogive percentile graph serves as a convenient scale that lets an individual's test score be instantly translated into a rank within the normed group — related