July 2009

While the validity of any exam is really the accurate or valid interpretation of exam scores, such interpretations depend upon the content and constructs measured in the exam.  The appropriate knowledge and skill must be tested to achieve valid scores.

Tara McNaughton
Manager, Test Development and Analysis

Practice Analysis Issues and Methods
The primary purpose of certification exams is distinguishing individuals capable of practicing safely and effectively from those who can not.  It is essential to ensure that these high stakes examinations are valid, reliable, and objective measures of candidate ability.

A valid test is one that measures what it's meant to measure, with the underlying goal to accurately interpret scores.  In order to make valid interpretations of scores, examinations should have 1) face validity, 2) content validity and 3) construct validity. Face validity simply implies that the test appears to cover appropriate areas of practice.  Content and construct validity suggest that the test measures the knowledge and skills pertinent to the field of practice.  A strong argument for content validity can be achieved by conducting a practice analysis.

The test blueprint supports the construct and content validity and is the basis for selecting items to be included on an exam.  The blueprint of the exam should mirror practice in the field not only in terms of the knowledge and skill sampled, but in the proportion, depth, and breadth of coverage.

The test blueprint can be created to the specification of current work in the field by means of a practice analysis.  The practice analysis solicits information from practicing professionals in the field concerning what they need to know, the tasks they perform, and the relative frequency or importance of each.  Multiple related tasks form a content area on the test blueprint.
In the development, data collection, and analysis of a practice analysis, the expertise of subject matter experts, practitioners, and psychometricians is required.  The subject matter experts often do the initial development of the survey by identifying the areas of knowledge and skill required to practice effectively.  Psychometricians can offer guidance in survey development.  Practitioners may be involved in the early stages of development through field tests or focus groups to further refine the survey.  Finally, a sample of practitioners is selected as the survey respondents.

The practice analysis can emphasize tasks and skills, as well as, the knowledge necessary to perform appropriately in the field.  The general format may be a list of tasks followed by likert scale responses designed to measure the frequency or importance of each for the professional in the field.  Another perspective on developing the practice analysis questionnaire is to focus on the knowledge, skills, and abilities needed for safe and effective practice within the field.  Developing this type of questionnaire focuses more on the personal attributes of the professional, as well as, the tasks being performed.

It can be difficult to encourage busy professionals to take the time to answer the survey.  Strategies to maximize response rates include limiting the length of the survey to a page or two which focus on the most critical issues.  Some organizations do follow ups such as multiple mailings, reminder phone calls and emails, or offering incentives for completing the survey.

The final step is the analysis of the data and the structuring of a usable test blueprint.  Psychometricians produce summary information concerning the measured importance and frequency of each item on the survey.  Subject matter experts review these results and make refinements in the final product based on their knowledge and experience in the field.

One interesting finding in the literature is that different approaches to practice analyses can produce very similar results.  The quality of expert judgments in developing and reviewing the analysis may influence the outcome more than the method or expense used for the practice analysis.  This underscores the importance of expert judgments in determining the eventual test blueprint that is developed.  While practitioners may be the best judges of frequency, some research indicates that measures of criticality may be best left to expert judgments.
Measurement Research Associates, Inc.
505 North Lake Shore Dr., Suite 1304
Chicago, IL  60611
Phone: (312) 822-9648     Fax: (312) 822-9650

Please help with Standard Dataset 4: Andrich Rating Scale Model

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 3rd. 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
in Spanish: Análisis de Rasch para todos, Agustín Tristán Mediciones, Posicionamientos y Diagnósticos Competitivos, Juan Ramón Oreja Rodríguez

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