I have a question about how to analyze some data. It involves the performance of two equally sized groups in a questionary with 30 arithmetic questions that I scored with two possible outcomes (correct/ incorrect) plus possible omissions (unsolved question). My first approach to these data has been to calculate each subjects' frequency of correct, incorrect and non-solved questions which I aimed to compare by means of a chi-square association test (plus an a posteriori inspection of the standardized residuals).
On a second step, as I do not expect differences between groups, I would like to observe whether participants (regardless of the group) provided more/ less correct answers depending on the type of arithmetic operation involved (addition, subtraction, multiplication or division). I intended to ascertain this question by means of chi-square goodness of fit and, again, an a posteriori inspection of the standardized residuals
However, I have been told that my approach might be incorrect because I should treat correct, incorrect and non-solved questions as interval variables. Therefore, I am quite puzzled at the moment and I would appreciate expert advice on the correct approach to deal with this two experimental situations.
(I am using SPSS, just in case this information might be relevant here)
thanks in advance!