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Last updated on October 3, 2025
Theoretical probability is a concept in statistics. It is used to calculate or analyze the likelihood of an event occurring. The calculations are done based on the known possible outcomes and mathematical principles. Here, the assumption is that all outcomes are equally likely. In this article, we’ll be learning about theoretical probability.
The objective of applying theoretical probability is to predict the likely outcome of an event. The prediction is based on mathematical reasoning and known outcomes, and not on actual experiments. In this process, we assume that all outcomes are equally likely. This technique is used when the outcomes are well-defined and predictable.
Make note of the following steps to find theoretical probability.
Step 1: Make sure the experiment that you are working on is well-defined. Determine the sample space by making a list of every experiment result.
Step 2: Determine which results satisfy the requirements of the event considered.
Step 3: Count all possible outcomes in the sample space.
Step 4: Count all favorable outcomes.
Step 5: Apply the formula:
P(E) = Number of Favorable Outcomes ÷ Total Number of Possible Outcomes.
Step 6: Put the probability in percentage or decimal or fraction format.
Theoretical probability is calculated using logic and known outcomes, while experimental and empirical probabilities rely on real-world trials and observed data, with empirical focusing on long-term observations.
Theoretical Probability | Experimental Probability | Empirical Probability |
Probability is based on reasoning, formulas, and known outcomes. | Probability is based on actual experiments or trials. | Probability is based on observed data collected from real-life and experiences. |
Formula is: P(E) = Favorable outcomes divided by total possible outcomes. |
Formula is: P(E) = Number of times event occurs divided by total number of trials. |
Formula is: P(E) = Frequency of event divided by total observed frequencies. |
Based on logic, models and mathematical rules. | Becomes more accurate with more trials. | Becomes more reliable with larger datasets. |
Here are some tips and tricks to master theoretical probability:
Theoretical probability: P(E) = Favorable outcomes/Total Outcomes
Complement Rule: P(Not A) = 1 − P(A)
When working on theoretical probability, students tend to make mistakes. Here, are some common mistakes and their solutions:
Theoretical probability can be used in many ways. Here are some examples:
What is the probability of getting heads when tossing a fair coin?
The probability of getting heads is ½
Identify the sample space:
S = {heads, tails}
Total outcomes = 2
Determine favorable outcomes:
Favorable outcome (heads) = 1
Calculate the probability:
P(heads) = 1/2
What is the probability of rolling a 4 on a fair six-sided die?
The probability of rolling a 4 is ⅙ on a fair six-sided die.
Identify the sample space:
S = {1, 2, 3, 4, 5, 6}
Total outcomes = 6
Favorable outcome:
Only one outcome is 4.
Probability:
P(4) = 1/6
What is the probability of drawing an Ace from a standard 52-card deck?
The probability of drawing an Ace is 1/13
Total outcomes:
There are 52 cards
Favorable outcomes:
Number of aces = 4
Probability:
P(Ace) = 4/52 = 1/13
What is the probability of obtaining a sum of 7 when rolling two fair six-sided dice?
The probability of obtaining a sum of 7 is 1/6
Total outcomes:
6 x 6 = 36
Favorable outcomes:
The pairs that sum to 7 are:
(1, 6), (2, 5), (3, 4), (4, 3), (5, 2), (6, 1) - 6 outcomes
Probability:
P(sum of 7) = 6/36 = 1/6
A spinner is divided into 8 equal sectors numbered 1 through 8. What is the probability of landing on sector 5?
The probability of landing on sector 5 is 1/8
Total outcomes:
8 sectors
Favorable outcomes:
Only sector 5 qualifies
Probability:
P(5) = 1/8
Jaipreet Kour Wazir is a data wizard with over 5 years of expertise in simplifying complex data concepts. From crunching numbers to crafting insightful visualizations, she turns raw data into compelling stories. Her journey from analytics to education ref
: She compares datasets to puzzle games—the more you play with them, the clearer the picture becomes!