Assessment of cognitive ability at conscription for the Danish army: Is a single total score sufficient?

Børge Priens Prøve (BPP) was developed for the Danish Army by psychologist Børge Prien in the 1950s, as a test of general cognitive ability for use at conscription for the Danish armed forces. The final BPP (1957) had four subtests; a Raven-like matrix subtest, and three subtests measuring verbal, numerical, and visuospatial ability. The BPP is a speeded test counting the number of correct responses within 45 minutes. Thus, we consider the BPP as a measure of "cognitive efficiency" rather than a pure measure of cognitive ability. The BPP is still in use.Using techniques available in 1960, Rasch concluded that the matrices and numerical tests appeared to satisfy the requirements of the Rasch (Probabilistic models for some intelligence and attainment tests, Danish Institute for Educational Research, Copenhagen; 1960) model, while the verbal and visuospatial tests did not. Since then, there have been, to our knowledge, no published studies of the psychometric scaling properties of the BPP, partly because the practice of the Danish draft board has been to record only the total score. We examine these properties by analysis of data from two cohorts (n = 9,491), using the Leunbach (A probabilistic measurement model for assessing whether two tests measure the same personal factor. The Danish Institute of Educational, Copenhagen, Denmark; 1976) model to assess whether the sum of the four subtests provides a statistically sufficient measure of a common latent trait. Since we found only weak evidence against fit to the Leunbach model, we claim that this warrants the use of a summarized total BPP score. We examined whether BPP subscales suffered from differential test functioning (DTF) relative to samples. Weak, and for practical purposes too weak, DTF was suggested for one subscale.