Let’s talk about DIF, baby!

Let’s talk about you and me (and our respective defining group memberships), let’s talk about all the good things (obtaining accurate scores) and the bad things (model misspecification) that may be. Let’s talk about DIF. Differential item functioning (DIF) is the psychometric jargon term for when items perform differently depending on characteristics of the person answering the item. Analyses for detecting DIF should be part of any initial calibration study of a COA, PRO, or test and are readily available … Read More

DIA 2016 Validity and Fit for Purpose

Drs. Wirth and Edwards of VPG will be joined by Drs. Ashley Slagle (Aspen Consulting) and Johnathan Rubright (National Board of Medical Examiners) when they discuss the roll of modern validity theory in evaluating a COA’s “fit for purpose”. Join them at DIA 2016 for Session #247 entitled “Fit for Purpose and Modern Validity Theory in PROs”. Learn more here.  

SPARQ: Is it useful for evaluating athleticism in the NFL?

A Little Background The SPARQ (Speed, Power, Agility, Reaction and Quickness) was developed as a standardized assessment of athleticism and now rests under the watchful eyes of NIKE (yes, that NIKE, the shoe company). The SPARQ has largely focused on selling stuff helping athletes (mainly high schoolers) “track their progress, measure improvement and benchmark against other athletes worldwide”1. The five events used to generate a general SPARQ rating are: 20 Meter Sprint/40 Yard Dash (Speed) Kneeling Power Ball Toss (Power) … Read More

That other can o’ worms

Last time, we had a riveting discussion about reliability and mentioned that validity is also something to consider when talking about tests/assessments/scales and the scores that come from them. So let’s do that. Previously, we used Score = truth + error to talk about measurement and the idea of reliability. That is, the more garbage (error) there is in your scores, the less reliable they will be. If your scores are full are noise, then your boat is already sunk. … Read More