Item Response Theory

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Introduction to Item Response Theory (IRT)

taught by Karen Schmidt

Aim of Course:

This online course, "Introduction to Item Response Theory (IRT)" will introduce you to the statistical basis for analyzing multiple-choice survey or test data - item response theory. This includes both dichotomous (two-outcome) data and polytomous (multiple outcome) data.  After introducing the key foundational concepts of traits, items, scales and scores, the course goes on to cover how to measure and model response data.  After taking this course, you should be able to understand how IRT is used, which models are appropriate for different contexts, how to construct scales, and understand output from IRT analyses.

Course Program:

Week 1:  Introduction, Theory, Concepts

  • History of IRT
  • Classical test theory and IRT
  • Why is effective measurement important?
  • Traits, items, scales and scores

Week 2: Measuring Dichotomous Responses

  • Adding item parameters: 1-, 2- and 3-Parameter models
  • What do the scores mean?
  • Dichotomous scale construction considerations

Week 3:  Measuring Polytomous Responses

  • The Graded Response Model
  • What do the scores mean?
  • Polytomous scale construction considerations

Week 4:  Practical Considerations and Applications of IRT

  • Assessing fit: How well do the items work?
  • Item and scale effectiveness: Dimensionality, Standard Errors, Information
  • Differential Item Functioning (DIF) and Computerized Adaptive Testing (CAT)


The homework in this course consists of short answer questions to test concepts, guided exercises in writing code and guided data analysis problems using


This course also has example software codes, supplemental readings available online and video lectures in each week.

Introduction to Item Response Theory (IRT)

Who Should Take This Course:

Researchers, social scientists, and education measurement scientists who want to learn about analyzing and creating better scales, tests, and questionnaires.



You should be familiar with introductory statistics.  Try these self tests to check your knowledge.

Organization of the Course: 

This course takes place online at the Institute for 4 weeks. During each course week, you participate at times of your own choosing - there are no set times when you must be online. Course participants will be given access to a private discussion board. In class discussions led by the instructor, you can post questions, seek clarification, and interact with your fellow students and the instructor.

At the beginning of each week, you receive the relevant material, in addition to answers to exercises from the previous session. During the week, you are expected to go over the course materials, work through exercises, and submit answers. Discussion among participants is encouraged. The instructor will provide answers and comments, and at the end of the week, you will receive individual feedback on your homework answers.

Time Requirement:
About 15 hours per week, at times of  your choosing.

Students come to the Institute for a variety of reasons. As you begin the course, you will be asked to specify your category:

  1. You may be interested only in learning the material presented, and not be concerned with grades or a record of completion.
  2. You may be enrolled in PASS (Programs in Analytics and Statistical Studies) that requires demonstration of proficiency in the subject, in which case your work will be assessed for a grade.
  3. You may require a "Record of Course Completion," along with professional development credit in the form of Continuing Education Units (CEU's).  For those successfully completing the course,  CEU's and a record of course completion will be issued by The Institute, upon request.

Course Text:

Course subject materials will be provided in each lesson. A suggested text (not required), for those who wish a more rigorous review of the concepts, is Fundamentals of Item Response Theory (Measurement Methods for the Social Science) by Ronald K. Hambleton, available on Amazon or on Sage.


You will use a hand calculator for some simple calculations (or Excel), and you will use the free R Studio statistical software program for obtaining IRT scores, item parameters, and response probabilities.  Its use is illustrated in the course. Exercises and materials will be provided to help you become introduced to R Studio with roughly 3 hours of additional work. Warning: The first week of the course has a comparatively heavy workload of regular course material, so if you need to learn R, be sure to appropriately budget your time.

Introduction to Item Response Theory (IRT)

February 17, 2017 to March 17, 2017August 18, 2017 to September 15, 2017February 16, 2018 to March 16, 2018August 17, 2018 to September 14, 2018

Course Fee: $589