Acceptable Variances

What are acceptable variances? The only answer that can be given to this question is, “It all depends.” If you are doing a well-defined construction job, the variances can be in the range of ± 3–5 percent. If the job is research and development, acceptable variances increase generally to around ± 10–15 percent. When the job is pure research, the sky is the limit. Imagine, for example, that you worked for a pharmaceutical company and your boss said, “Tell me how long it will take and how much it will cost for you to discover and develop a cure for AIDS.”

For every organization, you have to develop tolerances through experience. Then you start trying to reduce them. All progress is an attempt to reduce variation in what we do. We will never reduce it to zero, without eliminating the process altogether, but zero has to be the target.