The Accuracy of the Life Orientation Test–Revised (LOT–R) in Measuring Dispositional Optimism: Evidence From Item Response Theory Analyses

Abstract

The accuracy of the Life Orientation Test–Revised (LOT–R) in measuring dispositional optimism was investigated applying item response theory (IRT). The study was conducted on a sample of 484 university students (62% males, M age = 22.79 years, SD = 5.63). After testing the 1-factor structure of the scale, IRT was applied to evaluate the functioning of the LOT–R along the pessimism–optimism continuum. Item parameter estimates and the test information function showed that each item and the global scale satisfactorily measured the latent trait. Referring to the IRT estimated trait levels, the validity of the LOT–R was studied examining the relationships between dispositional optimism and psychological well-being, sense of mastery, and sense of coherence. Overall findings based on IRT analyses provide evidence of the accuracy of the LOT–R and suggest possible modifications of the scale to improve the assessment of dispositional optimism.

Acknowledgments

Francesca Chiesi and Caterina Primi are now with NEUROFARBA–Section of Psychology, University of Florence. Andrea Bonacchi is now at Centro Studi e Ricerche Synthesis, Florence, Italy.

Notes

IRT has been largely applied in the development of measures of ability and achievement. In this field, the term difficulty is more suitable to define the characteristic of the items. From a clinical standpoint, difficulty has been conceptualized as “severity” of the symptom described by the item. Between the two terms, in this study we chose severity to refer to the different levels of dispositional optimism.

Following the modification indexes, a covariation path was added between errors of Item 3 and Item 9. This inclusion was justified by the very similar meaning of the two items (“If something can go wrong for me, it will” and “I rarely count on good things happening to me”).

In this study, the full contingency table was not tested. The number of cells for the full contingency table is p = 5⁶ (where 6 represents the number of items, and 5 the number of response categories), and therefore the large majority of the cells had observed and expected frequencies of 0.

According to Baker (2001), values 0.01 to 0.24 are very low, 0.25 to 0.64 are low, 0.65 to 1.34 are moderate, 1.35 to 1.69 are high, and more than 1.7 are very high.

We can interpret the information magnitude computing the associated reliability (r = 1 – 1/Information). Thus, reliability was equal to or greater than .75 within the described range.