Definition of Probability (Leaving Cert Mathematics): Revision Notes

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Definition of Probability

Probability is the measure of how likely an event is to occur. Understanding how to calculate probabilities and the relationships between different events is fundamental in statistics.

Basic Probability Concepts

Probability of an Event (P(E))

The probability of an event EE is calculated as:

P(E)=Number of favourable outcomesTotal number of possible outcomes P(E) = \frac{\text{Number of favourable outcomes}}{\text{Total number of possible outcomes}}
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Example: The probability of rolling a 33 on a fair 66-sided die:

P(rolling a 3)=16 P(\text{rolling a 3}) = \frac{1}{6}

Complementary Events

The complement of an event EE is the event that EE does not occur.

If P(E)P(E) is the probability of EE , then the probability of the complement E′E' is:

P(E′)=1−P(E)P(E') = 1 - P(E)
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Example: If P(E)=0.4P(E) = 0.4 ,

then P(E′)=1−0.4=0.6P(E') = 1 - 0.4 = 0.6 .

Explore Leaving Cert Mathematics Model Answers by Topics

Fundamentals of Probability

The Basics of Counting

Permutations / Arrangements

The Basics of Probability

Combinations

Set Theory and Probability

Combined Events/Bernouilli Trials

Events

Expected Value

Explore Leaving Cert Mathematics Quizzes by Topics

Fundamentals of Probability

The Basics of Counting

Permutations / Arrangements

The Basics of Probability

Combinations

Set Theory and Probability

Combined Events/Bernouilli Trials

Events

Expected Value

Explore Leaving Cert Mathematics Flashcards by Topics

Fundamentals of Probability

The Basics of Counting

Permutations / Arrangements

The Basics of Probability

Combinations

Set Theory and Probability

Combined Events/Bernouilli Trials

Events

Expected Value

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