The most common way to create a labor standard is with a stopwatch – but it’s also the worst way. This method has many pitfalls that force a trade-off between time, cost and accuracy. Making matters worse, most people do not know that they are making a trade-off. Here are the top five reasons why stopwatch time studies are trouble:
1. It is easy for the observer to inaccurately capture the task. The observer needs to know when to start and stop the stopwatch and perform the action the same way for each observation. If the stopwatch starts or ends early or late, it affects the accuracy of the observation. This problem is compounded if you’re using a team of observers, as each person may have a different opinion of when the task is supposed to start or stop.
2. The person being observed skews the results. Typically, the person being observed is nervous and feels pressure to perform. After all, how much do you like it when someone watches you while you work? Often, the subject will work quickly to try and impress the observer. Or, the person being observed may work slowly and deliberately to show how diligent he or she is. Regardless, the subject is not performing the task as he or she normally would. This results in an inaccurate measurement.
3. It takes a lot of observations to accurately measure a task. For the reasons above and more, it takes hundreds if not thousands of observations to accurately measure a task. Most organizations are not willing to spend the time and money required to record enough observations. So, they settle for a “good enough” labor standard, forgetting that a small over or under allocation of labor can have a big impact on labor costs, quality, safety or customer service.
4. Task variations need to be measured separately. A task is not always performed the same way. Available equipment, the layout of the workplace and other factors mean that the same task takes different amounts of time in different locations. Significant variations need to be measured separately, adding more time, effort and cost to stopwatch time studies.
5. Tasks need to be remeasured when they change. Tasks change for lots of reasons: workspaces are reorganized, systems or equipment are updated and replaced, processes are redesigned, customer expectations change, and so on. When tasks change, the task needs to be remeasured all over again.
Ultimately, there are many reasons why the commonly used stopwatch study is a poor way to build labor standards. Companies, usually unknowingly, sacrifice time and/or cost for accuracy when they use this method for work measurement. Fortunately, there are other methods of creating more accurate labor standards for less time and cost, and I will tackle those methods in my next blog post.