Chapter 15: Problem 1
A die will be rolled 6 times. What is the chance of obtaining exactly 1 ace?
Short Answer
Expert verified
The probability of obtaining exactly 1 ace in 6 rolls is approximately 0.4019.
Step by step solution
01
Determine the Probability of Rolling an Ace
A standard die has six sides, numbered 1 through 6. An ace, in this context, refers to rolling a 1. Thus, the probability of rolling an ace on any single roll is \( \frac{1}{6} \).
02
Calculate the Probability of Not Rolling an Ace
If the probability of rolling an ace is \( \frac{1}{6} \), then the probability of not rolling an ace (rolling a 2, 3, 4, 5, or 6) is \( 1 - \frac{1}{6} = \frac{5}{6} \).
03
Use the Binomial Probability Formula
The scenario of rolling exactly 1 ace in 6 rolls follows a binomial distribution. The binomial probability formula is given by: \[ P(X = k) = \binom{n}{k} p^k (1-p)^{n-k} \]where:- \( n \) is the number of trials (6 rolls),- \( k \) is the number of successful outcomes (1 ace),- \( p \) is the probability of success on a single trial (\( \frac{1}{6} \)).
04
Calculate the Binomial Coefficient
For our problem, we need to calculate:\[ \binom{n}{k} = \binom{6}{1} = \frac{6!}{1!(6-1)!} = 6 \]
05
Substitute Values into the Binomial Formula
We substitute into the formula:\[ P(X = 1) = \binom{6}{1} \left( \frac{1}{6} \right)^1 \left( \frac{5}{6} \right)^{6-1} \]
06
Simplify the Expression
Simplifying gives:\[ P(X = 1) = 6 \times \frac{1}{6} \times \left( \frac{5}{6} \right)^5 = \left( \frac{5}{6} \right)^5 \]\[ P(X = 1) = \frac{3125}{7776} \approx 0.4019 \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Probability of Success
The probability of success is a crucial concept in any probability problem. For a binomial distribution, success is the event we are interested in. In the context of rolling a die, success is rolling an ace, which means getting a 1. Since a standard die has six numbers (1 to 6), the ace's probability is the probability of rolling a 1 on a single trial. So, we calculate the probability of success as:
- The number of favorable outcomes (rolling a 1)
- Divided by the total number of possible outcomes (6 sides)
Binomial Distribution
Binomial distribution is vital when dealing with probability problems that involve two potential outcomes: success or failure. It applies to scenarios where we perform a number of independent trials, each with the same probability of success.
In our problem of rolling a die, the binomial distribution can be used since each roll is an independent trial. The odds of rolling an ace do not change based on previous rolls. The parameters of a binomial distribution here include:
In our problem of rolling a die, the binomial distribution can be used since each roll is an independent trial. The odds of rolling an ace do not change based on previous rolls. The parameters of a binomial distribution here include:
- n: The total number of trials (6 rolls)
- p: The probability of success in each trial (chance of rolling an ace, \( \frac{1}{6} \))
Binomial Coefficient
The binomial coefficient is a factor that helps calculate the number of ways to achieve a certain number of successes in a series of trials. It provides the combination count, denoted by \( \binom{n}{k} \), and is pivotal in the binomial probability formula.
To find \( \binom{6}{1} \), which is how many ways we can get exactly one ace in six rolls, we use:\[\binom{6}{1} = \frac{6!}{1!(6-1)!}\]Where '!' denotes factorial, meaning to multiply the number by all positive integers less than it. Thus, \( 6! \) is \( 6 \times 5 \times 4 \times 3 \times 2 \times 1 \). Simplifying this gives us:\[\binom{6}{1} = 6\]The binomial coefficient shows there are 6 ways to roll one ace in 6 die rolls.
To find \( \binom{6}{1} \), which is how many ways we can get exactly one ace in six rolls, we use:\[\binom{6}{1} = \frac{6!}{1!(6-1)!}\]Where '!' denotes factorial, meaning to multiply the number by all positive integers less than it. Thus, \( 6! \) is \( 6 \times 5 \times 4 \times 3 \times 2 \times 1 \). Simplifying this gives us:\[\binom{6}{1} = 6\]The binomial coefficient shows there are 6 ways to roll one ace in 6 die rolls.
Probability Calculation
Once we've determined all the components, we can calculate the overall probability using the binomial probability formula. Here's how we bring it all together:The formula is:\[P(X = k) = \binom{n}{k} p^k (1-p)^{n-k}\]Where:
- n is the number of trials (6 dice rolls)
- k is the number of successful outcomes we want (1 ace)
- p is the probability of success (\( \frac{1}{6} \))
- \( (1-p) \) is the probability of failure (\( \frac{5}{6} \))