Theory of Constraints Handbook - James Cox Iii [507]
Let us revisit the lamp example from earlier in the chapter. At one point, we predicted that the power was out in the rest of the neighborhood. The street was dark, which was an additional effect of a neighborhood power outage. If we had looked outside and saw all of the streetlights and the lights in our neighbors’ homes brightly lit, then we would have known that there was not a power outage in the neighborhood. It would not have been an entity that existed in the situation we were analyzing.
2. Entity Clarity. Ensure each entity is stated clearly and concisely, as a simple yet complete sentence. A good test is that when you read the entity statement aloud, it needs no further explanation. An indicator that the statement is not yet clear enough is if you read it aloud to someone and feel compelled to explain further what it means.
3. Causality Existence. Validate that each cause and effect relationship identified in the analysis really does exist in the situation being analyzed. Even when you verify that the described elements do in fact exist in the situation or system being analyzed, it could very well be that the hypothesized cause-effect relationship between them does not. Here is an example.
I know a young woman who had a persistent headache. The headache was there when she woke up in the morning, throughout the day, and when she went to sleep at night. It simply did not go away. After a couple of weeks, she went to a local urgent care center.13 After asking a few questions and short examination, the doctor formulated his hypothesis and prescribed a solution accordingly. His hypothesis of the woman’s problem was that she had a simple tension headache. He prescribed a painkiller and told her to go home and relax. A simple analysis of the situation, in the doctor’s view, would have looked like Fig. 27-17a. Unfortunately, even though every entity in the tree did exist, and even though for most young adults stress is the cause for a headache, it was not in this case.
FIGURE 25-17 Validating “causality existence.”
A week or so and many pain pills later, the headache was not only still present, it had worsened, and she had become nauseated and disoriented. The young woman went to the emergency room at a local hospital. After a short interview and examination, the ER doctor formulated his hypothesis, which was that there was something physically going on in her head, possibly a tumor. He ordered a CT scan, which verified the existence of a quite large tumor in the left frontal lobe of her brain. (See Fig. 25-17b.)
I am not illustrating this case in order to pass judgment on either of the two doctors involved. I am illustrating this case in order to show that even though the same conditions might exist in two different realities, they have a cause-and-effect relationship in one of those realities and not another. The young woman did have some stress in her life, and she did have a headache. Tension is the cause for headaches often, but not always.14
Check the causality! It doesn’t take long to ask any or all of these questions: Why? ♦ How do I/we/you know? ♦ Is this always the case? ♦ Under what circumstances is this the case? ♦ Under what circumstances is this not the case? ♦ Oh, really? ♦Why?
4. Causality Clarity. Ensure each cause-effect relationship is modeled clearly and concisely. A good test is to read aloud the relationship as an “if-then” statement or as a “because” statement. An indicator that the cause-and-effect relationship is not yet clear enough is if you read it aloud to someone and feel compelled to explain further what it means. For instance, look at Fig. 25-18. The cause-and-effect relationships would be read as:
If [B] and [C], then [A]; or [A] exists because [B] and [C].
Additionally, if [D], then [A]; or [A] also exists because [D].
FIGURE 25-18 Cause clarity.