Mathematics
Grade 11
15 min
Graph a discrete probability distribution
Graph a discrete probability distribution
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Introduction & Learning Objectives
Learning Objectives
Define a discrete random variable and its probability distribution.
Construct a probability distribution table for a given discrete random variable.
Verify that a function or table represents a valid probability distribution.
Graph a discrete probability distribution using a histogram or bar chart.
Interpret the key features of a graphed distribution, such as its shape and center.
Calculate the expected value (mean) of a discrete random variable from its distribution table.
Use a graphed distribution to determine the probability of an event.
Ever wondered what the chances are of winning different prizes in a carnival game? 🎡 Graphing probabilities can help you see if the game is truly in your favor!
This tutorial will teach you how to take a set of ou...
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Key Concepts & Vocabulary
TermDefinitionExample
Discrete Random VariableA variable, typically denoted by X, that can take on a finite or countably infinite number of distinct values. These values are often integers that result from counting something.Let X be the number of heads obtained when flipping a coin three times. The possible values for X are {0, 1, 2, 3}.
Probability DistributionA table, formula, or graph that describes the probability for each possible value of a random variable.For a single fair die roll, the distribution table would list the outcomes {1, 2, 3, 4, 5, 6} and the probability for each, which is 1/6.
Probability Mass Function (PMF)A function, denoted P(X = x), that gives the probability that a discrete random variable X is exactly equal to some value x.If X is the result of a fair die roll,...
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Core Formulas
Conditions for a Valid Probability Distribution
1. 0 ≤ P(X = x) ≤ 1 for all values of x. \n 2. Σ P(X = x) = 1
These two conditions must be met for any discrete probability distribution. The first rule states that every probability must be between 0 and 1, inclusive. The second rule states that the sum of the probabilities for all possible outcomes must equal 1.
Formula for Expected Value (Mean)
μ = E[X] = Σ [x * P(X = x)]
To calculate the expected value, you multiply each possible value (x) of the random variable by its corresponding probability P(X = x), and then sum all of these products together.
4 more steps in this tutorial
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Challenging
A batch of 20 computer chips contains 4 defective chips. You randomly select 3 chips without replacement. Let X be the number of defective chips selected. Calculate the expected value, E[X].
A.0.6
B.0.5
C.0.75
D.0.4
Challenging
The graph of a probability distribution for X={1, 2, 3, 4} is shown. The bar heights are P(1)=0.1, P(2)=p, P(3)=0.4, P(4)=0.2. The expected value E[X] is known to be 2.8. What is the value of the missing probability, p?
A.0.1
B.0.2
C.0.3
D.0.4
Challenging
Let X be the random variable representing the absolute difference of the numbers shown when two fair six-sided dice are rolled. Which statement best describes the shape of the graph of the probability distribution of X?
A.Uniform, as all differences are equally likely.
B.Left-skewed, with the highest probability at X=1.
C.Symmetric and bell-shaped, centered around X=2.5.
D.Right-skewed, with the highest probability at X=5.
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