Math Problem Statement

The random variable X ~ B(12, 0.3). Find: (a) P(X ≤ 2) (b) P(X < 6) (c) P(X ≥ 7)

Solution

The problem asks to solve three probability questions for a binomial distribution:

The random variable XB(12,0.3)X \sim B(12, 0.3), which means XX follows a binomial distribution with parameters n=12n = 12 (the number of trials) and p=0.3p = 0.3 (the probability of success in each trial).

The binomial probability mass function (PMF) is given by: P(X=k)=(nk)pk(1p)nkP(X = k) = \binom{n}{k} p^k (1-p)^{n-k} where (nk)\binom{n}{k} is the binomial coefficient.

We are asked to find the following:

(a) P(X2)P(X \leq 2)

This is the cumulative probability for XX being less than or equal to 2: P(X2)=P(X=0)+P(X=1)+P(X=2)P(X \leq 2) = P(X = 0) + P(X = 1) + P(X = 2)

(b) P(X<6)P(X < 6)

This is the cumulative probability for XX being less than 6: P(X<6)=P(X5)=P(X=0)+P(X=1)+P(X=2)+P(X=3)+P(X=4)+P(X=5)P(X < 6) = P(X \leq 5) = P(X = 0) + P(X = 1) + P(X = 2) + P(X = 3) + P(X = 4) + P(X = 5)

(c) P(X7)P(X \geq 7)

This is the complement of P(X6)P(X \leq 6): P(X7)=1P(X6)P(X \geq 7) = 1 - P(X \leq 6)

Let me calculate each of these probabilities for you.The probabilities for the binomial distribution XB(12,0.3)X \sim B(12, 0.3) are:

(a) P(X2)=0.2528P(X \leq 2) = 0.2528

(b) P(X<6)=0.8822P(X < 6) = 0.8822

(c) P(X7)=0.0386P(X \geq 7) = 0.0386

Would you like more details on any of the steps or explanations?

Here are five follow-up questions you might consider:

  1. What is the probability that X=3X = 3 for this binomial distribution?
  2. How does changing the value of pp affect these probabilities?
  3. Can you calculate P(X=5)P(X = 5) directly?
  4. How do you calculate the mean and variance of a binomial distribution?
  5. What is the probability of getting more than 4 successes in this binomial experiment?

Tip: The binomial cumulative distribution function (CDF) is useful when you want to calculate probabilities for ranges of values, not just individual outcomes.

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Math Problem Analysis

Mathematical Concepts

Probability
Binomial Distribution
Cumulative Probability

Formulas

P(X = k) = (n choose k) * p^k * (1 - p)^(n - k)
P(X ≤ k) = sum from i=0 to k of P(X = i)
P(X ≥ k) = 1 - P(X ≤ k - 1)

Theorems

Binomial Probability Theorem

Suitable Grade Level

Grades 10-12