An electricity company supplies power to consumers in the Eastern region of a country. When the demand for power exceeds the capacity of the cheapest generating station asecond station is brought 'on-line.' One of the company's managers makes a daily judgmentabout the probability that the second station will be required at least once in the following day. The records of his judgments are given below for a period of 600 days.

Probability assessed by manager 0.2 0.5 0.8 1.0 Number of days this probability 40 160 180 120 100 judgment was made Number of days second station was 50 110 110 100 used