A Rasch analysis to determine the difficulty of the National Senior Certificate Mathematics examination
Abstract
The National Senior Certificate (NSC) examinations were written for the second time
in 2009 amid much criticism. In this study, scripts of candidates who wrote the NSC
Mathematics examinations (papers 1 and 2) in 2009 were used as data to analyse
the marks scored and then polytomous Rasch analysis was conducted for all the subquestions
to determine the level of difficulty of the questions. The purpose of applying
Rasch measurement models is to explore the extent to which a test or an examination
and its associated data set permit the interpretation of an underlying linear scale of
ability against which to interpret overall performance and item difficulty. In the NSC
data, some questions discriminated well at the lower-ability levels of candidates, but
no questions were found to discriminate among higher-ability candidates.