Math Problem Statement

Let X ~ B(8, 0.7) and the possible values of the random variable X are 0, 1, 2, 3, 4, 5, 6, 7, 8. Find P(X = 4), P(X >= 6), P(X > 5), P(3 <= X <= 7)

Solution

We are given a binomial distribution XB(8,0.7)X \sim B(8, 0.7), where n=8n = 8 and p=0.7p = 0.7. The possible values of the random variable XX are 0,1,2,3,4,5,6,7,80, 1, 2, 3, 4, 5, 6, 7, 8. We are asked to find the following probabilities:

Binomial probability mass function:

The formula for a binomial probability is: P(X=k)=(nk)pk(1p)nkP(X = k) = \binom{n}{k} p^k (1 - p)^{n - k} where:

  • nn is the number of trials,
  • kk is the number of successes,
  • pp is the probability of success in each trial.

Now, let's compute each probability step by step.

1) P(X=4)P(X = 4)

We calculate P(X=4)P(X = 4) using the binomial probability formula: P(X=4)=(84)(0.7)4(0.3)4P(X = 4) = \binom{8}{4} (0.7)^4 (0.3)^4

2) P(X6)P(X \geq 6)

To find P(X6)P(X \geq 6), we need to sum the probabilities of X=6,7,8X = 6, 7, 8: P(X6)=P(X=6)+P(X=7)+P(X=8)P(X \geq 6) = P(X = 6) + P(X = 7) + P(X = 8) We will calculate each of these using the binomial formula.

3) P(X>5)P(X > 5)

This is the probability that XX is greater than 5, which includes X=6,7,8X = 6, 7, 8: P(X>5)=P(X=6)+P(X=7)+P(X=8)P(X > 5) = P(X = 6) + P(X = 7) + P(X = 8) This is the same as P(X6)P(X \geq 6), so we will reuse the result from part (2).

4) P(3X7)P(3 \leq X \leq 7)

This requires summing the probabilities from X=3X = 3 to X=7X = 7: P(3X7)=P(X=3)+P(X=4)+P(X=5)+P(X=6)+P(X=7)P(3 \leq X \leq 7) = P(X = 3) + P(X = 4) + P(X = 5) + P(X = 6) + P(X = 7)

I'll now compute these probabilities.Here are the results for the given probabilities:

  1. P(X=4)=0.1361P(X = 4) = 0.1361
  2. P(X6)=0.5518P(X \geq 6) = 0.5518
  3. P(X>5)=0.5518P(X > 5) = 0.5518 (same as P(X6)P(X \geq 6))
  4. P(3X7)=0.9311P(3 \leq X \leq 7) = 0.9311

Would you like more details or clarification on any of these steps?

Here are five related questions for further exploration:

  1. How do the values of pp and nn affect the shape of the binomial distribution?
  2. What is the expected value and variance of a binomial distribution?
  3. How would you calculate P(X5)P(X \leq 5) for this distribution?
  4. What is the cumulative distribution function (CDF) of a binomial distribution, and how is it used?
  5. How do you approximate a binomial distribution using a normal distribution for large nn?

Tip: In binomial problems, cumulative probabilities can often be computed more efficiently using tables or software, especially for larger nn.

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Math Problem Analysis

Mathematical Concepts

Probability Theory
Binomial Distribution

Formulas

P(X = k) = (n choose k) * p^k * (1 - p)^(n - k)

Theorems

Binomial Theorem

Suitable Grade Level

Grades 10-12