Math Problem Statement

I have 18 black slots, 18 red slots, and 2 green. I roll 38 times, what is the probability of the ball going in the green slot 5 or more times

Solution

To solve this problem, we are dealing with a binomial probability distribution because we have a fixed number of trials (38 rolls), two possible outcomes for each trial (the ball either goes into a green slot or it does not), and the probability of success remains the same for each roll.

Key Information:

  • Total number of trials (rolls): n=38n = 38
  • Number of green slots: 2 (out of 38 slots)
  • Probability of landing in a green slot: p=238=119p = \frac{2}{38} = \frac{1}{19}
  • Number of green slots we want: 5 or more times.

Binomial Distribution Setup:

The binomial probability of exactly kk successes (green slots) in nn trials is given by the formula:

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

Where:

  • (nk)\binom{n}{k} is the binomial coefficient, calculated as n!k!(nk)!\frac{n!}{k!(n-k)!}.
  • p=119p = \frac{1}{19} is the probability of success (ball going into the green slot).
  • 1p=18191 - p = \frac{18}{19} is the probability of failure (ball not going into the green slot).
  • n=38n = 38 is the total number of trials (rolls).
  • kk is the number of successful outcomes (green slots) we're interested in.

Calculation:

We need to calculate the probability that the ball goes into the green slot 5 or more times out of 38 rolls. This is:

P(k5)=1P(k<5)P(k \geq 5) = 1 - P(k < 5)

Where:

P(k<5)=P(k=0)+P(k=1)+P(k=2)+P(k=3)+P(k=4)P(k < 5) = P(k = 0) + P(k = 1) + P(k = 2) + P(k = 3) + P(k = 4)

We'll now compute the binomial probability for P(k=0),P(k=1),P(k=2),P(k=3),P(k=4)P(k = 0), P(k = 1), P(k = 2), P(k = 3), P(k = 4) and then subtract their sum from 1.

Let me calculate this for you. scipy.stats as stats

Given data

n = 38 # number of trials p = 1 / 19 # probability of green slot k_max = 4 # maximum number of successful outcomes (for less than 5)

Calculate the cumulative probability for k = 0, 1, 2, 3, 4

P_k_less_than_5 = stats.binom.cdf(k_max, n, p)

Probability of 5 or more green slots

P_k_greater_or_equal_5 = 1 - P_k_less_than_5 P_k_greater_or_equal_5The probability that the ball goes into the green slot 5 or more times out of 38 rolls is approximately 0.0478, or about 4.78%.

Would you like a more detailed breakdown of the individual probabilities for k=0,1,2,3,4k = 0, 1, 2, 3, 4? Or do you have any other questions?

Here are 5 related questions to explore further:

  1. How do you calculate binomial probabilities for different values of kk?
  2. What happens to the probability as the number of green slots increases?
  3. How does the binomial distribution relate to other probability distributions like the normal distribution?
  4. How do you calculate the expected number of green slots in 38 rolls?
  5. What are the implications of the Central Limit Theorem for binomial probabilities when nn is large?

Tip: In real-world scenarios, when nn is large and pp is small, the binomial distribution can be approximated using the Poisson distribution for easier calculations.

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Math Problem Analysis

Mathematical Concepts

Probability Theory
Binomial Distribution
Combinatorics

Formulas

P(k) = C(n, k) * p^k * (1 - p)^(n-k)
C(n, k) = n! / (k!(n-k)!)
P(k ≥ 5) = 1 - P(k < 5)

Theorems

Binomial Theorem
Law of Total Probability

Suitable Grade Level

Undergraduate / Advanced High School (Grades 11-12)