The Revised Osterlind Index. A Comparative Analysis in Content Validity Studies
Keywords:Content Validity, Osterlind Index, Rating Scales, Empirical Evidence, Comparison
Agencies:This study forms part of the results obtained in research project PSI2011-29587, funded by Spain’s Ministry for Science and Innovation.
A procedure commonly used to obtain empirical evidence in content validity studies is the calculation of the Osterlind index after gathering the expert opinions about the adequacy of the items to measure a particular dimension of the tool. The aim of this work is to compare the results obtained when experts score the degree of suitability item-dimension on the traditional 3-point rating scales with the results obtained using, alternatively, 5-point ones. 105 participants valued, on 5-point rating scales, the fitness item-dimension of 31 items to 7 dimensions that composed a questionnaire to measure satisfaction with the training received. These marks were also transformed into 3-point rating scales. Comparison between Osterlind indexes calculated using scores from 5 and 3-point rating scales shows that the new propose is more conservative than the classic procedure; i.e., items considered adequate using 3-point rating scales were removed using 5-point rating scales.