- Probability is a quantitative measure of certainty.
- Any activity associated to certain outcome is called a random experiment e.g.,
(i) tossing a coin,
(ii) throwing a dice,
(iii) selecting a card.
- Outcome associated with an experiment is called an event. e.g.,
(i) Getting a head on tossing a coin,
(ii) getting a face card when a card is drawn from a pack of 52 cards.
- The events whose probability is one are called sure/certain events.
- The events whose probability is zero are called impossible events.
- An events with only one possible outcome is called an elementary event.
- In a given experiment, if two or more events are equally likely to occur or have equal probabilities, then they are called equally likely events.
- Probability of an event always lies between 0 and 1.
- Probability can never be negative.
- A pack of playing cards consist of 52 cards which are divided into 4 suits of 13 cards each. Each suit consists of an ace, one king, one queen, one jack and 9 other cards numbered from 2 to 10. Four suits are spades, hearts, diamonds and clubs.
- King, queen and jack are face cards.
- The sum of the probabilities of all elementary events of an experiment is 1.
- Two events A and B are said to be complementary to of each other if the sum of their probabilities is 1.
- Probability of an event E, denoted as P(E), is given by :
- For an event E, P(E) = 1- P(E), where the event E representing not E' is the complement of the event E.
- For, A and B two possible outcomes of an event,
(i) If P(A) > P(B), then event A is more likely to occur than event B.
(ii) If P(A) = P(B), then events A and B are equally likely to occur.
