Investigating The Central Tendency Effect Among Raters in Complex Problem-Solving Skills in Physics Essay Items: An Application of Many-Facet Rasch Measurement

The study sought to investigate the central tendency effect among raters in complex problem-solving skills in physics essay items using Many-Facet Rasch Measurement. This became necessary because the central tendency effect can affect students' scores. The research design adopted for this study is a descriptive research design based on the survey method. The population of the study comprised eighty-eight (88) public schools in all the local government areas with a physics student population of 3642 students and ninety-four (94) physics teachers in all the Senior Secondary Schools in Uyo Senatorial District for the 2022/2023 academic session. 364 SS3 physics students and 37 physics teachers from the 31 selected secondary schools in Uyo Senatorial District were sampled using a multistage sampling technique for effective selection. The multi-stage sampling technique was adopted for the study. The instrument used for data collection was the Physics Achievement Test (PAT) obtained from WAEC and NECO 2020 Physics Essay items. However, the reliability coefficient of 0.91 and 0.90 respectively. The finding revealed that there was no central tendency effect error committed by individual raters when rating complex problem-solving skills in WAEC and NECO 2020 physics Essay Items. Also, reveals there is a significant difference at the rater's group level exhibiting central tendency effect when rating complex problem-solving skills between WAEC and NECO 2020 physics Essay Items which implies that there is no group-level central tendency effect present among raters when rating complex problem-solving skills between WAEC and NECO 2020 physics Essay Items. The researchers concluded that rater effects are sources of variance in performance ratings that are associated with the rater's behaviour and not the actual performance of the ratee. It was recommended that to prevent the central tendency effect, it is important for superior raters to regularly observe their subordinates throughout the evaluation period and keep notes for future reference.