I am having a problem with calculating total scores for my measuring instruments on SPSS. If a case has a missing value on one item the total score for that case is not calculated. Does anyone know where the problem is and how do I handle this?
Avoid using arithmetic operators (e.g. V1 + V2 + V3) and use functions instead (e.g sum(v1, v2, v3)). There are obvious issues calculating total scores when you have missing data that you'll need to address. Possible approaches depending on your data would be to take a measure of central tendency rather than the sum (you'll need to decide how many missing values a case can have before it's considered invalid) or impute missing values.