Probability

The concept of probability is not a foreign to health workers. For example we may hear a physician say that a patient has 50-50
chance surviving from a certain operation, or physician may say that a patient has 95% a particular disease. Most people express
probabilities in terms of percentages. But, it is more convenient to express probabilities as fractions. Thus, we may measure the
probability of the occurrence of some event by a number between 0 and 1.
The more likely the event, the closer the number is to one. An event that can’t occur has a probability of zero, and an event that
is certain to occur has a probability of one.
1.Equally likely outcomes:
Are the outcomes that have the same chance of occurring.
2.Mutually exclusive:
Two events are said to be mutually exclusive if they cannot occur
simultaneously.
The universal Set (S): The set all possible outcomes.
The empty set ? : Contain no elements.
The event E : is a set of outcomes in universal set which has a certain characteristic.
Probability may be categorized into:
1- Classical probability:
If an event can occur in (N) mutually exclusive and equally likely ways, and if (m) of these possess a characteristics, (E), the probability of occurrence of (E) is equal to: P (E) = m / N.
For example, in the rolling of a dice
each of the six sides is equally
likely to be observed. So,
the probability that a 4 will be
observed is equal to 1/6.