Math Problem Statement

Let >= be "greater than or equal", <= be "less than or equal". The random variable X has a binomial distribution with n = 10 and p = 0.5. Which in is TRUE? Choose the best in the following statements. Select one:

P (X <= 2) = 0.0547

All of the others

P(X = 5) = 0.2461

P (X >= 9) = 0.0107

Solution

We are given that XX is a binomial random variable with n=10n = 10 trials and p=0.5p = 0.5 probability of success.

We can calculate the probability for each statement using the binomial probability formula:

P(X=k)=(nk)pk(1p)nkP(X = k) = \binom{n}{k} p^k (1-p)^{n-k}

where n=10n = 10 and p=0.5p = 0.5.

Let's evaluate each of the statements one by one:

1. P(X ≤ 2) = 0.0547

The cumulative probability P(X2)P(X \leq 2) is the sum of the individual probabilities from P(X=0)P(X = 0) to P(X=2)P(X = 2). We can calculate these terms:

  • P(X=0)=(100)(0.5)0(0.5)10=0.0009765625P(X = 0) = \binom{10}{0} (0.5)^0 (0.5)^{10} = 0.0009765625
  • P(X=1)=(101)(0.5)1(0.5)9=0.009765625P(X = 1) = \binom{10}{1} (0.5)^1 (0.5)^9 = 0.009765625
  • P(X=2)=(102)(0.5)2(0.5)8=0.0439453125P(X = 2) = \binom{10}{2} (0.5)^2 (0.5)^8 = 0.0439453125

Summing these up:

P(X2)=0.0009765625+0.009765625+0.0439453125=0.05468750.0547P(X \leq 2) = 0.0009765625 + 0.009765625 + 0.0439453125 = 0.0546875 \approx 0.0547

So, this statement is true.

2. P(X = 5) = 0.2461

We calculate P(X=5)P(X = 5) using the binomial formula:

P(X=5)=(105)(0.5)5(0.5)5=(105)(0.5)10P(X = 5) = \binom{10}{5} (0.5)^5 (0.5)^5 = \binom{10}{5} (0.5)^{10}

P(X=5)=10!5!5!(0.5)10=252×11024=0.246093750.2461P(X = 5) = \frac{10!}{5!5!} (0.5)^{10} = 252 \times \frac{1}{1024} = 0.24609375 \approx 0.2461

So, this statement is true.

3. P(X ≥ 9) = 0.0107

To calculate P(X9)P(X \geq 9), we need to find the sum of the probabilities for P(X=9)P(X = 9) and P(X=10)P(X = 10):

  • P(X=9)=(109)(0.5)9(0.5)1=10×11024=0.009765625P(X = 9) = \binom{10}{9} (0.5)^9 (0.5)^1 = 10 \times \frac{1}{1024} = 0.009765625
  • P(X=10)=(1010)(0.5)10=1×11024=0.0009765625P(X = 10) = \binom{10}{10} (0.5)^{10} = 1 \times \frac{1}{1024} = 0.0009765625

Summing these:

P(X9)=0.009765625+0.0009765625=0.01074218750.0107P(X \geq 9) = 0.009765625 + 0.0009765625 = 0.0107421875 \approx 0.0107

So, this statement is true.

4. All of the others

Since we have verified that all of the individual statements are true, this statement is also true.

Conclusion:

The correct answer is All of the others.


Would you like further clarification on any of these calculations? Here are some follow-up questions for deeper understanding:

  1. What is the general binomial probability formula, and how is it derived?
  2. How do we calculate cumulative probabilities like P(Xk)P(X \leq k)?
  3. What is the interpretation of a binomial distribution in real-life examples?
  4. How can we use a binomial distribution to model experiments with more trials or different probabilities?
  5. What are other methods for calculating binomial probabilities (e.g., using statistical software or tables)?

Tip: When calculating binomial probabilities, it’s helpful to use a calculator or statistical software for quick results, especially when the calculations involve large numbers.

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Math Problem Analysis

Mathematical Concepts

Probability
Binomial Distribution

Formulas

P(X = k) = C(n, k) * p^k * (1-p)^(n-k)
C(n, k) = n! / (k!(n-k)!)

Theorems

Binomial Probability Theorem

Suitable Grade Level

Grades 9-11