1. A tech company organises weekly productivity workshops for groups of 20 employees.

The company provides all necessary resources for these workshops.

The manager wants to test a new time-management technique to see if it is more effective than the current method.

He decides on the following plan:

• Before the workshop, each of the 20 employees will complete a questionnaire about their current productivity and stress levels.

• The 20 employees will be divided into two groups of 10 people: a test group and a control group.

• The test group will be trained in the new time-management technique during the workshop.

• The control group will continue with the current time-management method.

• After the workshop, and after a week spent using the time-management techniques for their work, each of the 20 employees will again complete a questionnaire about their productivity and stress levels.

• The productivity and stress levels of the two groups after the workshop and week's work will be compared.

Explain briefly why a control group should be used.