Researchers at IBM think that employees who get to choose their own working hours will be more satisfied than those who do not.
To test this idea, IBM employees at the Dallas facility are told that they can chose their own hours. Six months later, the satisfaction level of employees in the Dallas facility is compared to employees in the Knoxville facility. The employees in the Knoxville facility are considered the:
Based on the scenario being described within the question it can be said that the employees in the Knoxville facility are considered the control group. In research studies this group is a group separated from the rest of the experiment in order for the independent variable to not be able to affect that group or the results. Which is why in this scenario the Knoxville facility was left out of the study, therefore making it the control group.
