Differential item functioning in the Figure Classification Test.
- Authors: Van Zyl, E. , Visser, D.
- Date: 1998
- Subjects: Psychometric instruments , Mantel-Haenszel chi-square technique
- Type: Article
- Identifier: uj:6372 , http://hdl.handle.net/10210/1116
- Description: The elimination of unfair discrimination and cultural bias of any kind, is a contentious workplace issue in contemporary South Africa. To ensure fairness in testing, psychometric instruments are subjected to empirical investigations for the detection of possible bias that could lead to selection decisions constituting unfair discrimination. This study was conducted to explore the possible existence of differential item functioning (DIF), or potential bias, in the Figure Classification Test (A121) by means of the Mantel-Haenszel chi-square technique. The sample consisted of 498 men at a production company in the Western Cape. Although statistical analysis revealed significant differences between the mean test scores of three racial groups on the test, very few items were identified as having statistically significant DIF. The possibility is discussed that, despite the presence of some DIF, the differences between the means may not be due to the measuring instrument itself being biased/ but rather to extraneous sources of variation, such as the unequal education and socio-economic backgrounds of the racial groups. It was concluded that there is very little evidence of item bias in the test.
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Energy generation from full strength domestic wastewater using a sandwich dual chamber microbial fuel cell with an uncatalyzed mesh current collector cathode
- Authors: Adeniran, J.A. , De Koker, J.J. , Arotiba, O.A. , Van Zyl, E. , Du Plessis, S.
- Date: 2015
- Subjects: Microbial fuel cells , Power generation , Mesh current collector cathodes , Wastewater
- Language: english
- Type: article
- Identifier: http://hdl.handle.net/10210/15528 , uj:15671 , Adeniran, J.A. et al. 2015. Energy generation from full strength domestic wastewater using a sandwich dual chamber microbial fuel cell with an uncatalyzed mesh current collector cathode. International journal of green energy
- Description: A sandwich domestic wastewater fed dual-chamber microbial fuel cell (MFC) was designed for energy generation and wastewater treatment. Power density for the MFC increased with increasing domestic wastewater concentration, reaching a maximum of 251 mW/m2 for full strength wastewater (3400 mg/L chemical oxygen demand (COD)) at a current density of 0.054 mA/cm2 at an external resistance of 200Ω. These values dropped to 60 mW/m2 (76% lower) and 0.003 mA/cm2 using wastewater 91% diluted to 300 mg/L COD. Maximum removals were: of COD, 89%; nitrite, 60%; nitrate, 77%; total nitrogen, 36%; and phosphate, 26%.
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