The Post-Study System Usability Questionnaire (PSSUQ) is a post-task measurement tool used to assess the usability of the system. The third current version includes 16 statements. Each statement has a likert scale ranging from 1 (totally agree) to 7 (not at all agree). Each statement also has the NA option (not applicable).
The PSSUQ has an overall score calculated by averaging the scores assigned to the statements.
The user is strongly in agreement on each statement. The overall score of the PSSUQ is therefore 1.
PSSUQ also has subscales for system utility (SysUse), quality of information (InfoQual) and quality of interface (IntQual). Their scores are calculated as follows:
- SysUse: calculating the average of the scores of readings 1 to 6
- InfoQual: average the scores of the statements 7 to 12
- IntQual: calculating the average of the scores of statements 13 to 15.
But how do I handle the statements that the user thinks are not applicable? Do they get the value 0 or do I simply ignore them from the calculation? For example, in IntQual which contains only three statements if NA gets the value 0:
The user strongly agrees on two statements and one statement does not apply. The IntQual score is 0.667.
If NA is rejected:
The user strongly agrees on two statements and one statement does not apply, the IntQual score is equal to 1.