Chapter 9: Problem 4
What is the expected value of one roll of a fair six-sided die?
Short Answer
Expert verified
The expected value of a roll of a fair six-sided die is 3.5.
Step by step solution
01
Understand the Concept of Expected Value
The expected value is a measure of the center of a probability distribution and represents a predicted average or mean outcome of a random process. For a discrete random variable, it is calculated as the sum of all possible values, each multiplied by the probability of its occurrence.
02
Identify Possible Outcomes and Their Probabilities
For a fair six-sided die, there are 6 possible outcomes when rolled: 1, 2, 3, 4, 5, and 6. Since the die is fair, each outcome has an equal probability of occurring, which is \( \frac{1}{6} \).
03
Calculate the Expected Value
To find the expected value, multiply each outcome by its probability and sum the results: \[E(X) = 1 \times \frac{1}{6} + 2 \times \frac{1}{6} + 3 \times \frac{1}{6} + 4 \times \frac{1}{6} + 5 \times \frac{1}{6} + 6 \times \frac{1}{6}\]This simplifies to:\[E(X) = \frac{1 + 2 + 3 + 4 + 5 + 6}{6} = \frac{21}{6} = 3.5\]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Probability Distribution
A probability distribution is a statistical function that describes all the possible values and likelihoods that a random variable can take within a given range. In simpler terms, it is a mathematical description of the probabilities of occurrence of different possible outcomes.
When we talk about rolling a die, this distribution tells us the probabilities associated with each of the six potential results. Probability distributions can be classified into two main types: discrete and continuous. A six-sided die is an excellent example of a discrete probability distribution because the die can only land on one of six distinct faces.
When we talk about rolling a die, this distribution tells us the probabilities associated with each of the six potential results. Probability distributions can be classified into two main types: discrete and continuous. A six-sided die is an excellent example of a discrete probability distribution because the die can only land on one of six distinct faces.
- Each face has a probability of \(\frac{1}{6}\) because the die is fair.
- The sum of probabilities for all outcomes in a probability distribution is always equal to 1.
Discrete Random Variable
A discrete random variable is a type of random variable that has a countable number of possible values. Unlike continuous random variables, which can take an infinite number of values within a range, discrete random variables have specific, distinct values.
When rolling a six-sided die, the outcome is a discrete random variable. The die can land on any of the six sides, each side representing a different possible value, namely 1 through 6.
When rolling a six-sided die, the outcome is a discrete random variable. The die can land on any of the six sides, each side representing a different possible value, namely 1 through 6.
- Each roll of a die results in one of the discrete outcomes: 1, 2, 3, 4, 5, or 6.
- The probability of each number appearing is the same, which aligns with the concept of a fair die.
Fair Die
A fair die is an idealized die where each face has an equal probability of landing face up. When rolling a fair six-sided die, each side or face has a probability of \(\frac{1}{6}\) of coming up. This fairness ensures that any outcome's occurrence is purely random, preventing bias in any of the results.
The concept of a fair die is very important in probability and statistics as it ensures that the probability distribution is uniform.
The concept of a fair die is very important in probability and statistics as it ensures that the probability distribution is uniform.
- A fair die exhibits perfect symmetry in terms of how probabilities are distributed across the possible outcomes.
- When calculating expected values with a fair die, each face contributes equally to the result.
Outcomes and Probabilities
Outcomes are the possible results of a random experiment, while probabilities measure the likelihood of each specific outcome occurring. When dealing with a fair six-sided die, the possible outcomes are numbered from 1 to 6. Each of these numbers represents the potential result from a roll.
The probability of each outcome is the same because the die is fair. Each outcome has a probability of \(\frac{1}{6}\).
The probability of each outcome is the same because the die is fair. Each outcome has a probability of \(\frac{1}{6}\).
- An outcome of 1 has a \(\frac{1}{6}\) probability, similarly for outcomes 2, 3, 4, 5, and 6.
- By ensuring each side has equal likelihood, computing an expected value becomes straightforward, as no single outcome is favored over another.