From All the Employees in a Company, a Small Group $\bar { X }$

From all the employees in a company, a small group was selected to participate in a study of employee satisfaction. The results of the study were to be generalized to all the employees of the company. To find the variability in satisfaction, the investigator should compute

A) $\bar { X }$
B) S
C) $\hat { S }$
D) $\sigma$ .