When I was a senior in high school, I took Probability and Statistics for my math class, instead of Calculus. I thought it would be an easy alternative that would further my ambitions of slacking off during my senior year. At the same time, my father, John Walker, was working on the 310 Cleaning Times book.

One day, he tapped me on the shoulder and said he had a job for me. He knew that I needed of a final project for stats class, and he was in need of a formula for predicting cleaning times in square feet per hour. What I didn’t realize at the time is that project would stick with me for the rest of my career.

Cleaning times and tasks are among the most misinterpreted data sets in the industry — many times misapplied, used to make inaccurate comparisons, or misused altogether. But there’s no magic to understanding cleaning times.

It’s important for you, the cleaning manager, to understand how to perform your own time and motion studies.

You don’t need to hire an expert, or even be one, to determine your own cleaning times. In fact, there’s a simple recipe for performing a time/motion study. You’ll need: an open, 1,000-square-foot space (or a fixture count, if working with restroom tasks); a tape measure; painter’s tape; a stopwatch or video camera (I prefer the latter, as it helps mitigate any disputes); if possible, three different people to perform the tasks; and the proper tools/equipment to perform the work three to five times.

To get started, take an inventory of cleaning tasks that you’re going to study. I prefer to evaluate single tasks at a time (i.e. vacuuming carpet using a 14-inch upright vacuum) because it’s easier to keep work organized. Instruct your worker to perform the work at a productive, but comfortable pace to cover the entire 1,000-square-foot area. Make note of any variations in methods or motion — they will be useful if you encounter any substantial time discrepancies.

Next, observe and record at least three to five different times per person in your test — people tend to pick up the pace as they become used to their working space. Once these have been completed, record the times in minutes for each trial and then determine an overall average.

Finally, you’ll want to make adjustments for any constant variables (travel speeds, filling times, emptying buckets, etc.) if they apply to the task you’re evaluating.