Math Problem Statement

Assume the random variable X has a binomial distribution with the given probability of obtaining a success. Find the following probability, given the number of trials and the probability of obtaining a success. Round your answer to four decimal places.

P(X≤2) , n=6 , p=0.3

Solution

To solve for P(X2)P(X \leq 2) for a binomial distribution with parameters n=6n = 6 trials and p=0.3p = 0.3 as the probability of success, we can use the binomial probability formula:

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

  • n=6n = 6 is the number of trials,
  • p=0.3p = 0.3 is the probability of success,
  • kk is the number of successes,
  • (nk)\binom{n}{k} is the binomial coefficient.

To find P(X2)P(X \leq 2), we need to calculate:

P(X2)=P(X=0)+P(X=1)+P(X=2)P(X \leq 2) = P(X = 0) + P(X = 1) + P(X = 2)

We'll compute each term:

  1. For P(X=0)P(X = 0): P(X=0)=(60)(0.3)0(0.7)6=11(0.7)6=0.117649P(X = 0) = \binom{6}{0} (0.3)^0 (0.7)^6 = 1 \cdot 1 \cdot (0.7)^6 = 0.117649

  2. For P(X=1)P(X = 1): P(X=1)=(61)(0.3)1(0.7)5=60.3(0.7)5=60.30.16807=0.302526P(X = 1) = \binom{6}{1} (0.3)^1 (0.7)^5 = 6 \cdot 0.3 \cdot (0.7)^5 = 6 \cdot 0.3 \cdot 0.16807 = 0.302526

  3. For P(X=2)P(X = 2): P(X=2)=(62)(0.3)2(0.7)4=150.09(0.7)4=150.090.2401=0.324135P(X = 2) = \binom{6}{2} (0.3)^2 (0.7)^4 = 15 \cdot 0.09 \cdot (0.7)^4 = 15 \cdot 0.09 \cdot 0.2401 = 0.324135

Now, summing these probabilities:

P(X2)=0.117649+0.302526+0.324135=0.744310P(X \leq 2) = 0.117649 + 0.302526 + 0.324135 = 0.744310

Thus, P(X2)0.7443P(X \leq 2) \approx 0.7443.

Answer: P(X2)0.7443P(X \leq 2) \approx 0.7443

Let me know if you would like further details or explanations on any part!


Further questions for you:

  1. How does the binomial distribution behave with different values of pp?
  2. What would the probability be if the number of trials were increased to n=10n = 10?
  3. How can the cumulative binomial probability be calculated using a statistical table?
  4. Can the binomial distribution approximate a normal distribution in any cases? If so, when?
  5. How does the standard deviation of a binomial distribution change with varying nn and pp?

Tip: When calculating binomial probabilities by hand, make sure to carefully compute the binomial coefficients, as small errors can accumulate. Using a calculator or statistical software is a great way to ensure accuracy!

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Math Problem Analysis

Mathematical Concepts

Binomial Distribution
Probability
Combinatorics

Formulas

P(X = k) = \binom{n}{k} p^k (1-p)^{n-k}
P(X ≤ k) = P(X = 0) + P(X = 1) + ... + P(X = k)

Theorems

Binomial Theorem

Suitable Grade Level

Grades 10-12