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.



Rasch Publications
Rasch Measurement Transactions (free, online) Rasch Measurement research papers (free, online) Probabilistic Models for Some Intelligence and Attainment Tests, Georg Rasch Applying the Rasch Model 2nd. Ed., Bond & Fox Best Test Design, Wright & Stone
Rating Scale Analysis, Wright & Masters Introduction to Rasch Measurement, E. Smith & R. Smith Introduction to Many-Facet Rasch Measurement, Thomas Eckes Invariant Measurement: Using Rasch Models in the Social, Behavioral, and Health Sciences, George Engelhard, Jr. Statistical Analyses for Language Testers, Rita Green
Rasch Models: Foundations, Recent Developments, and Applications, Fischer & Molenaar Journal of Applied Measurement Rasch models for measurement, David Andrich Constructing Measures, Mark Wilson Rasch Analysis in the Human Sciences, Boone, Stave, Yale

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Coming Rasch-related Events
July 28 - Nov. 22, 2014, Mon.-Sat. On-line course: Introduction to Rasch Measurement Theory (D. Andrich, I. Marais) www.education.uwa.edu.au/ppl/courses
Aug. 2-6, 2014, Sat.-Wed. PROMS2014, Guangzhou, China: Sat.-Sun. workshops; Mon.-Wed. symposium, www.confchina.com
Aug. 8 - Sept. 5, 2014, Fri.-Fri. On-line workshop: Many-Facet Rasch Measurement (E. Smith, Facets), www.statistics.com
Aug. 11-15, 2014, Mon.-Fri. On-line short course: Applied Measurement with jMetrik (P. Meyer). curry.virginia.edu/community-programs/conferences/jMetrik/
Sept. 3-5, 2014, Wed.-Fri. IMEKO International Measurement Confederation Symposium, Madeira Island, Portugal, www.imekotc7-2014.pt
Sept. 10-12, 2014, Wed.-Fri. In-person workshop: Introductory Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric
Sept. 12 - Oct. 24, 2014, Fri.-Fri. On-line workshop: Rasch Applications, Part I: How to Construct a Rasch Scale (W.P. Fisher), www.statistics.com
Sept. 15-17, 2014, Mon.-Wed. In-person workshop: Intermediate Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric
Sept. 18-19, 2014, Thurs.-Fri. In-person workshop: Advanced Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric
Sept. 30, 2014, Tues. Submission deadline: 6th Rasch Conference: Sixth International Conference on Probabilistic Models for Measurement in Education, Psychology, Social Science and Health, Cape Town, South Africa www.rasch.co.za/conference.php
Oct. 3, 2014, Fri. Submission deadline: IOMC 2015: International Outcomes Measurement Conference, Chicago IL www.jampress.org
Oct. 8-10, 2014, Wed.-Fri. IACAT Conference: International Association of Computerized Adaptive Testing, Princeton, NJ, iacat.org/conference
Oct. 17 - Nov. 14, 2014, Fri.-Fri. On-line workshop: Practical Rasch Measurement - Core Topics (E. Smith, Winsteps), www.statistics.com
Nov. 14, 2014, Fri. In-person workshop: IX Workshop on Rasch Models in Business Administration, Tenerife, Canary Islands, Spain, www.institutos.ull.es/viewcontent/institutos/iude/46416/es
Dec. 3-5, 2014, Wed.-Fri. In-person workshop: Introductory Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric
Jan. 2 - Jan. 30, 2015, Fri.-Fri. On-line workshop: Practical Rasch Measurement - Core Topics (E. Smith, Winsteps), www.statistics.com
Jan. 12-14, 2015, Mon.-Wed. 6th Rasch Conference: Sixth International Conference on Probabilistic Models for Measurement in Education, Psychology, Social Science and Health, Cape Town, South Africa www.rasch.co.za/conference.php
March 11-13, 2015, Wed.-Fri. In-person workshop: Introductory Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric
March 20, 2015, Fri. UK Rasch User Group Meeting, London, United Kingdom, www.rasch.org.uk
March 26-27, 2015, Thur.-Fri. In-person workshop: Introduction to Rasch Measurement with Winsteps (W. Boone), Cincinnati, raschmeasurementanalysis.com
April 16-20, 2015, Thurs.-Mon. AERA Annual Meeting, Chicago IL www.aera.net
April 21-22, 2015, Tues.-Wed. IOMC 2015: International Outcomes Measurement Conference, Chicago IL www.jampress.org
May 13-15, 2015, Wed.-Fri. In-person workshop: Introductory Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric
May 18-20, 2015, Mon.-Wed. In-person workshop: Intermediate Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric
Sept. 9-11, 2015, Wed.-Fri. In-person workshop: Introductory Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric
Sept. 14-16, 2015, Mon.-Wed. In-person workshop: Intermediate Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric
Sept. 17-18, 2015, Thur.-Fri. In-person workshop: Advanced Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric
Dec. 2-4, 2015, Wed.-Fri. In-person workshop: Introductory Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric
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