Variation and Its Impact on Safety Management

Since no two things are exactly alike, variation affects us in every aspect of our lives. Surprisingly, most American managers still don't pay much attention to variation.

When they do look at it, they base their reaction on whether it is good or bad. For example, when the number of accidents goes up one month they start to wonder if something was done wrong in the safety program. What they don't realize is that there are at least two ways of interpreting variation.

Years ago, I presented to an operations manager a simple run chart of the number of workers' compensation injuries per month in his department. During the review of the data, the corporate risk manager interrupted the discussion and asked the manager what he did wrong in the month of June when the number of accidents was higher than the other months of the year.

Somewhat perplexed, the operations manager explained he did nothing different that month. All of the safety meetings were held and all safety duties were carried out the same way they were in all the other months. After an awkward moment, the risk manger replied, “You must have done something different. The figures don't lie.” Which reminded me of something Dr. W. Edwards Deming used to say: “So much misunderstanding in so few words.”

The risk manager was acting as though he could see something in the data the operations manager was missing. He told the production manager he should redouble his efforts to find out what went wrong in June. The risk manager was working from the premise that variation in the number of accidents (outcomes) is the indicator of good or bad performance. For him, good management involved demanding a detailed explanation about every single data point.

The risk manager's management method relies on judging performance by the numbers but not knowing what the numbers really mean. He had no idea what the statement “absence of a negative doesn't mean you have a positive” means.

When this view of variation by managers is carried further, it becomes the way they determine good or bad performance between departments, divisions or people. These managers focus on interpreting what they see, and labeling these observations as causes of problems. They spend no time examining the system because they have mistaken symptoms for causes. Their world is one of command and control, where it is assumed that when things go wrong, it is not the fault of the system but of the employees.

The risk manager had never learned how variation in outcomes is affected by common and special causes. Understanding this difference would have provided him with a better idea of how to react to variation.

COMMON AND SPECIAL CAUSES

The other way to interpret variation in performance is that variation stems from common and special causes. William Shewhart classified these causes as follows;

1. Common causes: Those causes that inherently are part of the process (or system) hour after hour, day after day and that affect everyone working in the process.

2. Special causes: Those causes that are not part of the process under normal circumstances and don't affect everyone.

For example, when employees are watching a safety presentation, their attention is affected by causes common to everyone in the audience. These could include the room temperature, the condition of the chairs, the delivery by the presenter, the lighting and noise from outside the room. These are common causes. There also are causes that affect how each individual will process the information delivered that are special for each person. These include hearing loss, lack of sleep the night before, eyesight and personal problems that are creating a distraction.

If the lack of attention is due to common causes, then the speaker and the program planner need to take these into consideration for future presentations. If lack of attention is from special causes, then the employees in the audience need to address them. It is important for managers to know if they are dealing with common or special causes when fixing problems in a constant cause system.

Common causes exist in any constant cause system. The best way to understand the performance of a system is to track its quality characteristics. Quality characteristics of work include things such as the color of parts, the fit and finish of final products and the number of accidents.