NCERT Book Class 11 Maths Probability Questions

16.1 Overview
Probability is defined as a quantitative measure of uncertainty – a numerical value that conveys the strength of our belief in the occurrence of an event. The probability of an event is always a number between 0 and 1 both 0 and 1 inclusive. If an event’s probability is nearer to 1, the higher is the likelihood that the event will occur; the closer the event’s probability to 0, the smaller is the likelihood that the event will occur. If the event cannot occur, its probability is 0. If it must occur (i.e., its occurrence is certain), its probability is 1.

16.1.1 Random experiment An experiment is random means that the experiment has more than one possible outcome and it is not possible to predict with certainty which outcome that will be. For instance, in an experiment of tossing an ordinary coin, it can be predicted with certainty that the coin will land either heads up or tails up, but it is not known for sure whether heads or tails will occur. If a die is thrown once, any of the six numbers, i.e., 1, 2, 3, 4, 5, 6 may turn up, not sure which number will come up.

(i) Outcome A possible result of a random experiment is called its outcome for example if the experiment consists of tossing a coin twice, some of the outcomes are HH, HT etc.

(ii) Sample Space A sample space is the set of all possible outcomes of an experiment. In fact, it is the universal set S pertinent to a given experiment. The sample space for the experiment of tossing a coin twice is given by S = {HH, HT, TH, TT}
The sample space for the experiment of drawing a card out of a deck is the set of all cards in the deck.

16.1.2 Event
An event is a subset of a sample space S. For example, the event of drawing an ace from a deck is A = {Ace of Heart, Ace of Club, Ace of Diamond, Ace of Spade}

16.1.3 Types of events
(i) Impossible and Sure Events The empty set φ and the sample space S describe events. In fact φ is called an impossible event and S, i.e., the whole sample space is called a sure event.

Please refer to attached file for NCERT Class 11 Maths Probability Questions