Safety and anxiety

With regard to the anxiety for physical damages, safety is equivalent to security and danger to anxiety. However, in the other cases, safety does not always mean security. Safety equipment, safety process, and safety plant imply harmless equipment, harmless process, and harmless plant, respectively. On the other hand, secure equipment, secure process, and secure plant should not only be harmless but should also guarantee peace of mind. 

Although the degree of danger generally increases in proportion to the probability of an undesirable event, the degree of anxiety will not be proportional 

People experience anxiety/expectation when there is a possibility that an undesirable/desirable event will occur. Anxiety/expectation can be discussed by using 

The anxiety is due to the existence of uncertainty regarding whether such an undesirable event occurs. The uncertainty is characterized by the probability of occurrence, P, and the probability of disappearance, (1 — P). The amount of uncertainty regarding whether the undesirable event occurs is expressed by the information entropy as 

H has the maximum value of In 2 at P = 1 /2, and the distribution of H becomes symmetric with respect to P = 1/2. By considering that (1 — P) implies the probability of disappearance of undesirable event, the amount of uncertainty becomes maximum when the probability of occurrence and probability of disappearance are equal. For the probabilities, there are two natural reference points— 

---