Chapter 6: Problem 25
A binomial probability experiment is conducted with the given parameters. Compute the probability of \(x\) success in the \(n\) independent trials of the experiment. \(n=7, p=0.5, x>3\)
Short Answer
Expert verified
The probability of more than 3 successes is 0.609375.
Step by step solution
01
Identify the Binomial Probability Formula
The binomial probability formula is given by \[ P(X = x) = \binom{n}{x} p^x (1-p)^{n-x} \] where \[ \binom{n}{x} = \frac{n!}{x!(n-x)!} \] represents the number of combinations.
02
Determine the Cumulative Probability
In this case, we need the probability of having more than 3 successes, which means we need to calculate the summation of probabilities for x = 4, 5, 6, and 7. This can be written as: \[ P(X > 3) = P(X = 4) + P(X = 5) + P(X = 6) + P(X = 7) \]
03
Compute Individual Probabilities
Compute each individual probability using the binomial formula: For \( x = 4 \):\[ P(X = 4) = \binom{7}{4} (0.5)^4 (0.5)^{7-4} \]For \( x = 5 \):\[ P(X = 5) = \binom{7}{5} (0.5)^5 (0.5)^{7-5} \]For \( x = 6 \):\[ P(X = 6) = \binom{7}{6} (0.5)^6 (0.5)^{7-6} \]For \( x = 7 \):\[ P(X = 7) = \binom{7}{7} (0.5)^7 (0.5)^{7-7} \]
04
Calculate Each Combination
Compute the combinations: \[ \binom{7}{4} = 35 \]\[ \binom{7}{5} = 21 \]\[ \binom{7}{6} = 7 \]\[ \binom{7}{7} = 1 \]
05
Substitute Values and Calculate
Substitute the values into the formula and calculate each probability:\[ P(X = 4) = 35 \times (0.5)^4 \times (0.5)^3 = 35 \times 0.0078125 = 0.2734375 \]\[ P(X = 5) = 21 \times (0.5)^5 \times (0.5)^2 = 21 \times 0.03125 = 0.21875 \]\[ P(X = 6) = 7 \times (0.5)^6 \times (0.5)^1 = 7 \times 0.015625 = 0.109375 \]\[ P(X = 7) = 1 \times (0.5)^7 \times (0.5)^0 = 1 \times 0.0078125 = 0.0078125 \]
06
Sum the Probabilities
Add all the individual probabilities together to get the total probability of having more than 3 successes:\[ P(X > 3) = 0.2734375 + 0.21875 + 0.109375 + 0.0078125 = 0.609375 \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Binomial Distribution
The binomial distribution is a discrete probability distribution. It describes the number of successes in a fixed number of independent trials. Each trial must have only two possible outcomes: success or failure.
To fully define a binomial distribution, you need two parameters:
To fully define a binomial distribution, you need two parameters:
- The number of trials (\( n \)
- The probability of success in a single trial (\( p \)
Probability Formula
The binomial probability formula is essential for solving any problem involving a binomial distribution. It allows us to calculate the probability of exactly \( x \) successes in \( n \) trials:
\[ P(X = x) = \binom{n}{x} p^x (1-p)^{n-x} \]
In the formula:
\[ P(X = x) = \binom{n}{x} p^x (1-p)^{n-x} \]
In the formula:
- \( \binom{n}{x} \) is the number of ways to choose \( x \) successes out of \( n \)
- \( p \) is the probability of success in each trial
- \( 1-p \) is the probability of failure in each trial
Combinations
The concept of combinations is crucial in binomial probability calculations. A combination represents the number of ways to choose a subset of items from a larger set, without considering the order. In mathematical terms, it is denoted by \( \binom{n}{x} \) and calculated using the formula:
\[ \binom{n}{x} = \frac{n!}{x!(n-x)!} \]
Here, \( n! \) represents the factorial of \( n \) (the product of all positive integers up to \( n \)), and similarly for \( x! \) and \( (n-x)! \).
In our problem:
\[ \binom{n}{x} = \frac{n!}{x!(n-x)!} \]
Here, \( n! \) represents the factorial of \( n \) (the product of all positive integers up to \( n \)), and similarly for \( x! \) and \( (n-x)! \).
In our problem:
- \( \binom{7}{4} = 35 \)
- \( \binom{7}{5} = 21 \)
- \( \binom{7}{6} = 7 \)
- \( \binom{7}{7} = 1 \)