Experiment in Probability

In this chapter we will learn the concept and types of experiment in probability.

The word ” experiment” is extensively used in probability chapter, so you need to understand the meaning and significance behind this to solve related problems.

What is experiment in probability ?

The operation which produce well defined outcomes are called experiment.

In an experiment, we can identify all the possible results even before performing the experiment.

For example;
(a) In the experiment of flipping a coin, we know beforehand that there are two possible outcomes, Head or Tail.

(b) In an experiment of choosing a color from rainbow, we know that there can be 7 possible outcomes (red, orange, yellow, green, blue, indigo and violet)

(c) In an experiment of throwing a dice, we know that there are 6 possible outcomes. ( from number 1 to number 6 )

In probability, the experiments are of two types;

(a) Deterministic experiments
(b) Random experiments

Let us learn about each of them in detail.

What is Deterministic experiments ?

The experiment whose result can be determined beforehand is called deterministic experiment.

For example;
(a) In an experiment of selecting triangle from different group, we can surely say that no matter which triangle we choose, the sum of angle will be 180 degree.

Hence, even before selecting the triangle, we know the end result.

(b) Sea, river and lake water are presented in a vessel.
In an experiment of getting chemical composition of randomly selected water, we know before hand that the chemical composition will be H2O.

As water chemical composition is universal, we knew the results beforehand.

What is Random experiment?

The experiment whose result cannot be determined beforehand is called random experiment.

The random experiment, if performed repeatedly under similar condition will give different result.

For example;

(a) Consider the experiment of tossing a coin.
We know the possible outcome can be “heads” or ” tails”. But we cannot know the result for next coin toss in advance.

(b) Picking a card from well shuffled deck.
We know that there are 52 different cards in a deck. But we cannot know which card will be selected in advance.

(c) Seats in theater
The experiment of selecting seats in theater is an random experiment. You cannot be definitely sure which seat you will get while booking tickets.

I hope you understand the above concept. Given below are solved problems for your practice.

Identify type of experiment in probability – Solved problems

(01) Given below are set of experiments. Identify if it is deterministic or random experiment.

(a) Dividing 16 by 2
(b) Waiting time for next train in station
(c) Selecting people for height measurement
(d) Direction of sun rise
(e) exam marks of random selected student in class


(a) Dividing 16 by 2

Every time you divide 16 by 2, you will get number 8 as solution.

Since the outcome can be determined beforehand, it is a deterministic experiment.

(b) Waiting time for next train in station

Every time you wait for next train, the waiting time will vary. Hence it is an random experiment.

(c) Selecting people for height measurement

On repeating the same experiment, you will get different heights. Hence, it is a random experiment.

(d) Direction of sun rise

Everyday the sun rises from east. Hence, it is an deterministic experiment.

(e) Exam marks of random selected student in class

Every time you run an experiment, you will run into different student with different marks.

Since the outcome cannot be predicted, it is a random experiment.

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