medium difficulty4 min

Experimental Probability

Experimental probability is the probability found from actual trials by dividing the number of times an event occurs by the total number of trials.

In one line: Experimental means evidence from trials, not only equal-looking possibilities.

Practice This Concept

Understand it

This probability comes from observed data. It may change when the experiment is repeated more times, especially when the number of trials is small.

Example

If a coin is tossed 50 times and heads appears 28 times, the experimental probability of heads is 28/50.

Formula and rule

Experimental probability = number of times the event occurs / total number of trials.

See it worked out

Follow the example line by line, then use the same method on new questions.

Worked example

1A spinner is spun 60 times and lands on red 18 times.
2Experimental probability of red = 18/60 = 3/10.

Method you can reuse

Find the event count, find total trials, write event count over total trials, and simplify if required.

Visual tip

A frequency table can be used to show outcomes and their observed counts.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

A die is thrown 40 times and 6 appears 7 times. What is the experimental probability of getting 6?

Think first, then show answer

The experimental probability of getting 6 is 7/40 because 6 appeared 7 times out of 40 actual trials.

Common wrong answer

Using 1/4 for red only because a spinner has four colours is wrong when the question asks for observed experimental probability.

Don't mix this up

Students often use the theoretical answer 1/2 even when the question gives actual trial results.

Exam tip

If the question says observed, recorded, surveyed, tossed many times, or experiment result, use the given data.

Write it in the exam

Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.

How CBSE asks it

Questions usually give a table of observed results and ask for probability based on that record.

1
Enough for 1 mark
Experimental probability is the probability found from actual trials by dividing the number of times an event occurs by the total number of trials.
2
Add for 2 marks
Example: If a coin is tossed 50 times and heads appears 28 times, the experimental probability of heads is 28/50.
3
Add for 3 marks
This probability comes from observed data.

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