Construct, item, and response bias across cultures in personality measurement

D.Phil.This study was done in order to investigate the presence and functioning of construct, item, and response bias across gender, ethnic, and language groups in a personality questionnaire. The Basic Traits Inventory (Taylor & De Bruin, 2006) was used as the personality assessment in this study, and is a South African-developed measure of the Big Five personality factors. This study made use of both traditional methods based on classical test theory and Rasch analysis from the item response theory genre. Comparison groups based on gender, ethnicity, and home language were specified for the analyses. The sample consisted of 6,112 students from a database of studies done using the Basic Traits Inventory. There were 2,080 men and 3,104 women in the sample, of which 1,240 were Black students and 1,139 were White students. The language groups were composed of English-speaking (n = 1,739), Afrikaans-speaking (n = 1,648), and Indigenous African language-speaking (n = 1,483) students. Some students did not indicate biographic details. The reliability of the Basic Traits Inventory was evaluated using both Cronbach’s alpha reliability coefficient and the person separation index (PSI) from the Rasch analysis. Both methods revealed similar indices of internal consistency. For the Big Five factors of the Basic Traits Inventory, the reliability estimates were similar across methods, and deemed satisfactory for the Extraversion (B = 0.90; PSI = 0.89), Neuroticism (B = 0.94; PSI = 0.93), Conscientiousness (B = 0.94; PSI = 0.92), Openness to Experience (B = 0.88; PSI = 0.85), and Agreeableness (B = 0.88; PSI = 0.86) scales. Three facet scales, namely Openness to Values, Straightforwardness, and Modesty, showed consistently lower than acceptable Cronbach alpha values across the comparison groups, indicating that scores on these facets should be interpreted with caution. From the Rasch analysis of each of the factors of the Basic Traits Inventory, it emerged that 35 of the 180 items showed some evidence of misfit, and specifically underfit. Of the 35 misfitting items, only 10 items showed signs of extreme underfit. iv There was very little evidence for item bias across all groups on each of the five factors of the Basic Traits Inventory. For the gender groups, there were three items with DIF contrast values larger than 0.5 logits across all five factors. For the ethnicity groups, eight of the items showed DIF contrast values larger than 0.5 logits. Only three items met the criteria for item bias in the language groups. Items O2 and O23 were judged to show item bias in both the ethnicity and language groups, and should be removed from future versions of the Basic Traits Inventory