I won't bore you with all the references to how multi-tasking produces waste. But do understand, the company policy to have very high utilization of staff creates the requirement for multi-tasking. Full utilization is not sustainable. Until you can lower utilization, thereby creating slack, you won't be learning and innovating. You can't be lean.
Make three columns on a page for the three projects X, Y and Z. For the first project (column) you'll write the numbers 1 – 10; in the second column write the letters A – J; and in the last column the Roman numerals I – X. You'll perform these three projects twice. Have someone time you.
Project X Project Y Project Z 1 A I 2 B II . . . . . . . . . 10 J X
The first time performing the projects do it in multi-tasking mode by taking the first step of each project by recording the first character for all three sequences, then the second character for all three and through to the tenth characters — row by row — until all three projects are completed.
On the second pass complete one project before going on to the next by recording one full sequence in a column, all the numbers, then all the letters, finally all the Roman numerals — column by column.
Now, compare your times. Also, note if you made any errors along the way.
I've used a number of exercises and examples to show the mal-effects of multi-tasking, however none are as powerful AND as easy to demonstrate as Clarke's three-column exercise. I'll post my results in a comment to this posting. Please share the results and reactions that you got. Thanks Clarke!