Measurement without Copper Instruments and Experiment without Complete Control

Extract

One basic reason that measurement in psychology requires statistics is that psychologists do not use copper instruments anymore, as they used to do in the nineteenth century. Instead, they determine test or total scores on the basis of miniature experiments with discrete outcomes, and use a variety of standard statististical techniques for reaching conclusions on the basis of observed data. Borsboom (2006) wants us to believe that psychologists are seriously misled in their hope that they can make progress this way, and recommends an invasion of psychometricians carrying IRT missiles and SEM guns into psychology.My prediction is that such an invasion would simply be ignored. That is not to say that whenever psychometric modeling really makes a difference, no attempts should be made to reach the mainstream of psychology. Indeed, many psychometric contributions that are obsolete according to Borsboom, like Cronbach’s alpha and exploratory factor analysis, in fact entered into the mainstream of psychology only because they tend to provide sensible answers to real problems, which cannot be easily surpassed.