What is a T score?


A T Score (sometimes hyphenated T-Score) is a common example of a scaled score in psychometrics and assessment.  A scaled score is simply a way to present scores in a more meaningful and easier-to-digest context, with the benefit of hiding the sometimes obtuse technicalities of psychometrics.  Therefore, a T Score is a standardized way that scores are presented to make them easier to understand.

What is a T Score?

A T score is a conversion of the standard normal distribution, aka Bell Curve.  The normal distribution places observations (of anything, not just test scores) on a scale that has a mean of 0.00 and a standard deviation of 1.00.  The T Score simply converts this to have a mean of 50 and standard deviation of 10.  This has two immediate benefits to most consumers:

  1. There are no negative scores; people generally do not like to receive a negative score!
  2. Scores are round numbers that generally range from 0 to 100, depending on whether 3, 4, or 5 standard deviations is the bound (usually 20 to 80); this somewhat fits with what most people expect from their school days, even though the numbers are entirely different.

The image below shows the normal distribution, labeled with the T Score and also Percentile Rank for interpretation.

T scores

How to interpret a T score?

As you can see above, a T Score of 40 means that you are approximately the 16th percentile.  A 70 means that you are approximately the 98th percentile – so that it is actually quite high though students who are used to receiving 90s will feel like it is low!

Since there is a 1-to-1 mapping of T Score to the other rows, you can see that it does not actually provide any new information.  It is simply a conversion to round, positive numbers, that is easier to digest.

Is a T Score like a t-test?

No.  Couldn’t be more unrelated.  Nothing like the t-test.

How do I implement with an assessment?

If you are using off-the-shelf psychological assessments, they will likely produce a T Score for you in the results.  If you want to utilize it for your own assessments, you need a world-class assessment platform like FastTest that has strong functionality for scoring methods and scaled scoring.  An example of this is below.

Scaled scores in FastTest


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Nathan Thompson, PhD

Nathan Thompson earned his PhD in Psychometrics from the University of Minnesota, with a focus on computerized adaptive testing. His undergraduate degree was from Luther College with a triple major of Mathematics, Psychology, and Latin. He is primarily interested in the use of AI and software automation to augment and replace the work done by psychometricians, which has provided extensive experience in software design and programming. Dr. Thompson has published over 100 journal articles and conference presentations, but his favorite remains https://pareonline.net/getvn.asp?v=16&n=1.

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