Mathematics
Grade 11
15 min
Write a discrete probability distribution
Write a discrete probability distribution
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1
Introduction & Learning Objectives
Learning Objectives
Define a discrete random variable and identify its possible values.
List the complete sample space for a simple random experiment.
Calculate the probability of each possible value of a discrete random variable.
Construct a table to represent a discrete probability distribution.
Verify that a table represents a valid probability distribution by checking its two core properties.
Interpret a discrete probability distribution to answer questions about the likelihood of events.
If you roll two dice, are you more likely to get a sum of 7 or a sum of 10? 🎲 Let's build the tool that answers this question precisely!
This tutorial will teach you how to create a discrete probability distribution, which is a fundamental tool in probability. It's essential...
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Key Concepts & Vocabulary
TermDefinitionExample
Random Variable (X)A variable whose value is a numerical outcome of a random phenomenon. We typically use a capital letter, like X, to denote it.If we flip a coin 3 times, we can define a random variable X to be the number of heads that appear. X can take the values 0, 1, 2, or 3.
Discrete Random VariableA random variable that can only take on a finite or countably infinite number of distinct values. You can 'count' the possible outcomes.The number of cars that pass through an intersection in one minute. You can have 10 cars or 11 cars, but not 10.5 cars.
Sample Space (S)The set of all possible outcomes of a random experiment.When rolling a single six-sided die, the sample space is S = {1, 2, 3, 4, 5, 6}.
Probability DistributionA table, formula, or graph t...
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Core Formulas
The Two Conditions for a Valid Discrete Probability Distribution
1. 0 ≤ P(X = x) ≤ 1 for all possible values of x.
This rule states that the probability for any single outcome must be a value between 0 and 1, inclusive. A probability cannot be negative or greater than 100%.
The Sum of Probabilities
2. Σ P(X = x) = 1
This rule states that if you add up the probabilities of all possible outcomes, the sum must be exactly 1. This ensures that your distribution accounts for the entire sample space.
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Challenging
A committee of 3 people is to be randomly selected from a group of 5 boys and 4 girls. If X is the random variable representing the number of girls on the committee, what is P(X = 2)?
A.30/81
B.5/14
C.6/84
D.1/2
Challenging
Two fair six-sided dice are rolled. Let the random variable Y be the absolute difference between the numbers on the two dice. What is P(Y=5)?
A.1/18
B.1/36
C.1/12
D.0
Challenging
From a standard 52-card deck, 3 cards are drawn without replacement. Let X be the number of face cards (Jack, Queen, King) drawn. What is P(X=2)? (There are 12 face cards in a deck).
A.66/22100
B.264/2210
C.132/5525
D.132/1105
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