contrasting groups cutscore

Contrasting Groups Method

The Contrasting Groups Method is a common approach to setting a cutscore.  It is very easy to do, but has the important drawback that some sort of “gold standard” is needed to assign examinees into categories such as Pass and Fail.  This “gold standard” should be unrelated to the test itself.

For example, suppose you wanted to set a cutscore on a practice test that is helping examinees determine if they are ready for a high-stakes certification test.  You might have past data for examinees who took both your practice exam and the actual certification test.  Their results from the certification test can be used to assign them to groups of Pass or Fail, and then you can evaluate the practice test score distributions for each group.  These distributions are typically smoothed, and their intersection represents an appropriate cutscore for the practice test.  In the example below, the two curves intersect near a score of 85, suggesting that this is an appropriate cutscore for the practice test that will closely predict the results of the official certification test.

I developed a simple tool in MS Excel that allows our psychometricians to easily produce both the smoothed and unsmoothed versions of this method, given nothing more than a list of practice test scores and “real” test classification for examinees.  If you think this method might be appropriate for your exams, please contact us at sales@assess.com and one of our consultants will get in touch with you.

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Nathan Thompson, PhD

Chief Product Officer at ASC
I am a psychometrician, software developer, author, and researcher, currently serving as Chief Product Officer for Assessment Systems Corporation (ASC). My mission is to elevate the profession of psychometrics by using software to automate the menial stuff like job analysis and Angoff studies, so we can focus on more innovative work. My core goal is to improve assessment throughout the world. I was originally trained as a psychometrician, doing an undergrad at Luther College in Math/Psych/Latin and then a PhD in Psychometrics at the University of Minnesota. I then worked multiple roles in the testing industry, including item writer, test development manager, essay test marker, consulting psychometrician, software developer, project manager, and business leader. Research and innovation are incredibly important to me. In addition to my own research, I am cofounder and Membership Director at the International Association for Computerized Adaptive Testing, You can often find me at other important conferences like ATP, ICE, CLEAR, and NCME. I've published many papers and presentations, and my favorite remains http://pareonline.net/getvn.asp?v=16&n=1.