I use a likert type questionnaire (7 point scale) in order to measure four variables: usefulness, ease of use, ease of learning and satisfaction. Hence in the questionnaire I have four different sub scales and each one has likert items which measure one variable.
I want to find the correlation between the variables. In order to do that, I sum the responses of the likert items for each sub scale and then i correlate the sums using Pearson's coefficients. Is it a good tactic?