The purpose of the study was to compare the effects on item bias of conventional testing procedures to the effects of two-stage testing procedures. It is conjectured that much of the measurement error identified as bias can be explained by factors, such as guessing or carelessness, attributable to inappropriate matching of test difficulty level and examinee ability level. Methods for detecting bias based on the-traditional definition of item difficulty fail to separate test characteristics from the ability distribution of the respondent sample. The separation of item and ability parameters, however, is an essential ingredient for an objective definition of bias. Such objectivity in measurement is provided by the Rasch latent trait model, which consequently was selected as the basis for this study. Three definitions of bias were considered, two of which were based on the Rasch model. The analyses were conducted using the scores of random subsamples (n=400 each) of black and white students on items selected from three reading subtests. The two-stage testing procedure was simulated using the real data set by "routing" students to one of three difficulty levels of the subtests based on their Rasch ability estimates as determined by a ten item routing test. Results for the two-stage testing procedure were compared with those from the conventional testing procedure at the subtest level. A reduction in the number of items identified as biased under conditions of appropriate matching of examinee ability levels and test difficulty levels was indicated by these analyses. Although the results are not conclusive, it is felt that individualizing according to the examinee's ability level offers promise in the direction of reading differential cultural measurement error. / Ph. D.

This study attempts to show that there is no significant difference in performance between volunteers and non-volunteers in terms of cooperation in a psychological experiment.

<p>The diversity embodying South Africa has emphasized the importance and influence of language in education and thus the additive bilingual programme is being implemented in the Eastern Cape by the ABLE project in order to realize the South African Language in education policy (LEiP). In accordance with this, the Woodcock Munoz Language Survey (which specializes in measuring cognitive academic language proficiency) was chosen as one of the instruments to evaluate the language outcomes of the programme and was adapted into South African English and isiXhosa. The current study was a subset of the ABLE project, and was located within the bigger project dealing with the translation of the WMLS into isiXhosa and the successive research on the equivalence of the two language versions. This study evaluated the structural equivalence of the English and isiXhosa versions of the WMLS on matched sample groups (n= 150 in each language group). Thus secondary data analysis (SDA) was conducted by analyzing the data in SPSS as well as CEFA (Comprehensive Exploratory Factor Analysis). The original data set was purposively sampled according to set selection criteria and consists of English and isiXhosa first language learners. The study sought to confirm previous research by cross-validating the results of structural equivalence on two subscales, namely the Verbal Analogies (VA) and Letter-Word Identification (LWI) subscale. The research design reflects psychometric test theory and is therefore located in a bias and equivalence theoretical framework. The results of the exploratory factor analysis found that one can only accept structural equivalence in the first factor identified in the VA subscale, while structural equivalence was found in the factor for the LWI subscale. The use of scatter-plots to validate the results of the exploratory factor analysis indicated that one can tentatively accept these results. The study thus contributed to the literature on the translation of the WMLS, and the adaptation of language tests into the indigenous languages of South Africa,as well as additive bilingual programmes.</p>

<p>The diversity embodying South Africa has emphasized the importance and influence of language in education and thus the additive bilingual programme is being implemented in the Eastern Cape by the ABLE project in order to realize the South African Language in education policy (LEiP). In accordance with this, the Woodcock Munoz Language Survey (which specializes in measuring cognitive academic language proficiency) was chosen as one of the instruments to evaluate the language outcomes of the programme and was adapted into South African English and isiXhosa. The current study was a subset of the ABLE project, and was located within the bigger project dealing with the translation of the WMLS into isiXhosa and the successive research on the equivalence of the two language versions. This study evaluated the structural equivalence of the English and isiXhosa versions of the WMLS on matched sample groups (n= 150 in each language group). Thus secondary data analysis (SDA) was conducted by analyzing the data in SPSS as well as CEFA (Comprehensive Exploratory Factor Analysis). The original data set was purposively sampled according to set selection criteria and consists of English and isiXhosa first language learners. The study sought to confirm previous research by cross-validating the results of structural equivalence on two subscales, namely the Verbal Analogies (VA) and Letter-Word Identification (LWI) subscale. The research design reflects psychometric test theory and is therefore located in a bias and equivalence theoretical framework. The results of the exploratory factor analysis found that one can only accept structural equivalence in the first factor identified in the VA subscale, while structural equivalence was found in the factor for the LWI subscale. The use of scatter-plots to validate the results of the exploratory factor analysis indicated that one can tentatively accept these results. The study thus contributed to the literature on the translation of the WMLS, and the adaptation of language tests into the indigenous languages of South Africa,as well as additive bilingual programmes.</p>

The traditional radiation testing of space electronics has been used for more than fifty years to support the radiation hardness assurance. Its typical goal is to ensure reliable operation of the spacecraft in the harsh environment of space. This PhD research looks into the radiation testing from a different perspective; the goal is to develop radiation testing methods that are focused not only on the reliability of the components but also on a continuous radiation-induced degradation of their performance. Such data are crucial for the understanding of the impact of radiation on the measurement uncertainty of data acquisition systems onboard research space missions.