The optional essay problem and the hypothesis of equal difficulty
By: Nancy L. Allen, Paul W. Holland, Dorothy T. Thayer
Contributors: Holland, Paul W.; Thayer, Dorothy T.; Educational Testing Service
Series: Program statistics research technical report -- no. 93-34; Research report -- no. 93-40; Research report (Educational Testing Service) -- RR-93-40
Publisher: Educational Testing Service
Published: 1993
Place of publication: Princeton, N.J
Language: eng
Number of pages: 37
Subjects: Examinations; Scoring
Notes: "August 1993."

Includes bibliographical references (p. 30-31).