A company is evaluating two different word processing packages for use by its clerical staff. Part of the evaluation is how quickly a test document can be entered correctly using the two programs. We have $20$ test secretaries$,$ and each secretary will enter the document twice, using each program once.

For each secretary$,$ toss a coin: the secretary will use the

programs in the orders AB and BA according to whether the coin is a head

or a tail, respectively.

Is the following statement about the experiment true or false?

The experimental units for this experiment are the secretaries$.$