Answer: It is not.
Explanation:
The salaries paid to the various departments of a company are usually different as some departments get paid more than others. For instance, in a manufacturing company, the R&D department would on average, get paid more than members of the Cleaning department.
Asking members of only one department therefore, about their pay satisfaction would not bring about a reasonable result because it would not be indicative of the thoughts of members of the other departments who are not being paid the same.