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According to the Mars Candy Company, the longrun percentages of various colors of M\&M milk chocolate candies are as follows: \(\begin{array}{llllll}\text { Blue: } & \text { Orange: } & \text { Green: } & \text { Yellow: } & \text { Red: } & \text { Brown: } \\ 24 \% & 20 \% & 16 \% & 14 \% & 13 \% & 13 \%\end{array}\) a. In a random sample of 12 candies, what is the probability that there are exactly two of each color? b. In a random sample of 6 candies, what is the probability that at least one color is not included? c. In a random sample of 10 candies, what is the probability that there are exactly 3 blue candies and exactly 2 orange candies? d. In a random sample of 10 candies, what is the probability that there are at most 3 orange candies? [Hint: Think of an orange candy as a success and any other color as a failure.] e. In a random sample of 10 candies, what is the probability that at least 7 are either blue, orange, or green?

Short Answer

Expert verified
a) Use multinomial probability; b) Use complement principle; c) Calculate binomial probability; d) Sum binomial probabilities; e) Evaluate cumulative probability.

Step by step solution

01

Understand the Multinomial Distribution

The problem involves multiple categories of candies, with specified probabilities for each color. The multinomial distribution models the probability of obtaining a certain number of outcomes in each category from a fixed number of trials. Here, each candy represents a trial, and the color corresponds to the outcome.
02

a. Use Multinomial Probability (2 of Each Color)

To find the probability of exactly two candies of each color out of 12, we use the multinomial probability formula: \[P(X_1 = 2, X_2 = 2, X_3 = 2, X_4 = 2, X_5 = 2, X_6 = 2) = \frac{12!}{2!2!2!2!2!2!} \cdot 0.24^2 \cdot 0.20^2 \cdot 0.16^2 \cdot 0.14^2 \cdot 0.13^2 \cdot 0.13^2\] Substitute and compute for the exact probability.
03

b. Probability of Missing at Least One Color

For a sample of 6, calculating the probability that at least one color is missing involves the complement of having all colors present. Use the complement principle: \[ P(\text{at least one color missing}) = 1 - \text{P(all colors appear)} \] Calculate \( P(\text{all colors appear}) \) using the multinomial probability for the scenario where at least one of each color is not included. This requires assessing distributions where at most 5 colors are involved.
04

c. Bivariate Binomial for Blue and Orange

For a sample size of 10, calculate the probability for exactly 3 blue candies and exactly 2 orange candies:\[P(B=3, O=2) = \frac{10!}{3!2!5!} \cdot 0.24^3 \cdot 0.20^2 \cdot (1-0.24-0.20)^5\]Complete the term for non-blue/non-orange candies and compute the probability.
05

d. At Most 3 Orange Candies

Treat orange candies as a success in binomial trials with parameters \( n=10 \) and probability \( p=0.20 \). Calculate cumulative probability up to 3: \[P(X \leq 3) = \sum_{k=0}^{3} \binom{10}{k} \cdot 0.20^k \cdot 0.80^{10-k}\]Compute this summation for each value of \( k \) from 0 to 3.
06

e. At Least 7 of Blue, Orange, or Green

Calculate the probability that at least 7 candies are either blue, orange, or green using a binomial approach where each is considered a 'success' with their combined probability:\[P(X \geq 7) = \sum_{k=7}^{10} \binom{10}{k} \cdot (0.24+0.20+0.16)^k \cdot (1-(0.24+0.20+0.16))^{10-k}\]Evaluate this expression by calculating probabilities for \( k \) from 7 to 10.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Probability Calculation
Probability calculation is the backbone of statistics and mathematics when determining the likelihood of outcomes, especially when dealing with events that have multiple possible results.
When calculating probability, it's important to understand the groundwork of
  • Event: A specific outcome or a set of outcomes of a random experiment.
  • Probability of an Event: Calculated as the ratio of the favorable outcomes to the total possible outcomes.
In our exercise concerning M&M candies, the probabilities of different colored candies represent individual events. For example, the probability that a single candy is blue is 24% or 0.24.
One of the calculations involved in the exercise is using the **multinomial distribution**. This type of distribution extends the binomial distribution concept to scenarios where there are more than two possible outcomes. Here, we have multiple colors, and we need to examine the probability of obtaining a specific quantity of each color out of a sample. Understanding probability calculations helps simplify these complex questions by providing a structured approach.
Binomial Probabilities
Binomial probabilities help us explore outcomes with exactly two possibilities, like success or failure. In our exercise, we sometimes treat finding M&Ms of certain colors as if they were successes in a binomial trial.
The key components of a **binomial distribution** are:
  • n: Number of trials (like picking 10 candies).
  • p: Probability of success on a single trial (like the probability of picking an orange candy).
  • X: Random variable representing the number of successes out of n trials.
When we talk about probability in terms of binomial outcomes, we often aim to calculate the probability of a certain number of successes.
For instance, in one exercise question, we calculate the likelihood of getting no more than three orange candies out of ten candies. This is achieved by summing up individual binomial probabilities for zero to three orange candies. Understanding binomial distributions is crucial when you're dealing with problems involving two possible outcomes.
Combinatorial Mathematics
Combinatorial mathematics comes into play when we deal with arrangements and selections in probability calculations. It involves understanding how to count combinations and permutations, vital for probability calculations involving multiple categories.
One of the main tools is the **factorial notation (!)**, used to calculate the number of ways to arrange a set of items. For example, in the multinomial probability equation \[\frac{12!}{2!2!2!2!2!2!}\] in our exercise, the factorial calculation helps determine the number of different ways to arrange our candies into specific counts.
Combinatorics also introduces the concept of the **binomial coefficient**, noted as \(\binom{n}{k}\) and defined as the number of ways to choose \(k\) successes out of \(n\) trials. These coefficients are crucial for binomial probabilities and are calculated as \[\binom{n}{k} = \frac{n!}{k!(n-k)!}\] Mastering combinatorial mathematics is essential for solving problems involving counting methods and probability calculations that require grouping or arrangement of objects such as candies, balls, or other discrete entities.

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Most popular questions from this chapter

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