Medieval Measurers

Definition of Objective Measurement

Objective measurement is the repetition of a unit amount that maintains its size, within an allowable range of error, no matter which instrument, intended to measure the variable of interest, is used and no matter who or what relevant person or thing is measured.

An objective measurement estimate of amount stays constant and unchanging (within the allowable error) across the persons measured, across different brands of instruments, and across instrument users. The goal of objective measurement is to produce a reference standard common currency for the exchange of quantitative value, so that all research and practice relevant to a particular variable can be conducted in uniform terms. Objective measurement research tests the extent to which a given number can be interpreted as indicating the same amount of the thing measured, across persons measured, and brands of instrument.

Our intuitions about measurement are confirmed with everyday trips to the grocery store. For instance, when selecting apples from a bin, one may readily see that three large apples might contain twice as much edible fruit as three small ones. To account for this difference, the cost is not proportionate with the actual, concrete number of apples, but with their abstract weight.

Most measurement efforts in the human sciences tally differently sized test or survey answers and stop there, mistakenly treating these concrete counts as abstract measures of amount. Over 70 years of objective measurement research and practice have established conclusively 1) the viability of scaling different instruments intended to measure a common variable onto a single reference standard ruler, and 2) the value of developing objective measurement-based construct theories.

The extent to which the unit amount remains constant within a particular range of error cannot be assumed. Research in objective measurement is largely a matter of asserting and testing hypotheses concerning the quantitative status of psychosocial variables. Such research might begin from an instrument, data, a theory, or some combination of these, but proceeds in a manner that uses each of these to check and improve the other two.

Objective measurement can be achieved and maintained employing a wide variety of approaches and methods. These include testing for concatenation, conjoint additivity, Guttman ordering, infinite divisibility, parameter separation or sufficiency. Objective measurement operates within the research traditions of fundamental measurement theory, item response theory, and latent trait theory.

Written by the Program Committee of the Institute for Objective Measurement. December 2000.

Coming Rasch-related Events
Feb 26 - June, 2018Online Advanced course in Rasch Measurement Theory (D.Andrich), University of Western Australia, Perth, Australia,
May 22 - 24, 2018, Tues.-Thur. EALTA 2018 pre-conference workshop (Introduction to Rasch measurement using WINSTEPS and FACETS, Thomas Eckes & Frank Weiss-Motz),
May 25 - June 22, 2018, Fri.-Fri. On-line workshop: Practical Rasch Measurement - Core Topics (E. Smith, Winsteps),
June 25 - 28, 2018, Mon.-Thur.Análisis de Rasch introductorio (en español). (Agustín Tristán), Instituto de Evaluación e Ingeniería Avanzada. San Luis Potosí, México.
June 27 - 29, 2018, Wed.-Fri. Measurement at the Crossroads: History, philosophy and sociology of measurement, Paris, France.,
June 29 - July 27, 2018, Fri.-Fri. On-line workshop: Practical Rasch Measurement - Further Topics (E. Smith, Winsteps),
July 25 - July 27, 2018, Wed.-Fri. Pacific-Rim Objective Measurement Symposium (PROMS), (Preconference workshops July 23-24, 2018) Fudan University, Shanghai, China "Applying Rasch Measurement in Language Assessment and across the Human Sciences",
July 29 - August 4, 2018 Vth International Summer School `Applied Psychometrics in Psychology and Education`, Institute of Education at the Higher School of Economics, St. Petersburg, Russia,
July 30 - Nov., 2018Online Introduction to Classical and Rasch Measurement Theories (D.Andrich), University of Western Australia, Perth, Australia,
Aug. 10 - Sept. 7, 2018, Fri.-Fri. On-line workshop: Many-Facet Rasch Measurement (E. Smith, Facets),
August 25 - 28, 2018, Sat.-Tue.Análisis de Rasch introductorio (en español). (Agustín Tristán), Instituto de Evaluación e Ingeniería Avanzada. San Luis Potosí, México.
Sept. 3 - 6, 2018, Mon.-Thurs. IMEKO World Congress, Belfast, Northern Ireland,
Oct. 12 - Nov. 9, 2018, Fri.-Fri. On-line workshop: Practical Rasch Measurement - Core Topics (E. Smith, Winsteps),

25 a 28 de junio de 2018. 25 a 28 de agosto de 2018.