Math Problem Statement

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Random Variables and Distributions Discrete probability distribution: Word problems Topic Progress 0 of 5 0/5

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Problem PageQuestion An number cube (a fair die) is rolled 3 times. For each roll, we are interested in whether the roll comes up even or odd. An outcome is represented by a string of the sort oee (meaning an odd number on the first roll, an even number on the second roll, and an even number on the third roll). For each outcome, let N be the random variable counting the number of even rolls in each outcome. For example, if the outcome is eoe, then =Neoe2. Suppose that the random variable X is defined in terms of N as follows: =X−2N2−4N3. The values of X are given in the table below. Outcome eeo ooe oee eee eoe eoo oeo ooo Value of X −3 −5 −3 3 −3 −5 −5 −3 Calculate the probabilities P=Xx of the probability distribution of X. First, fill in the first row with the values of X. Then fill in the appropriate probabilities in the second row. Value x of X P=Xx

Explanation

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Solution

Let's break down the problem step-by-step:

Problem Summary

  1. Experiment: A fair die is rolled 3 times.
  2. Outcome Representation: Each roll can be categorized as odd (o) or even (e).
    • An outcome, such as "oee," indicates odd on the first roll, even on the second, and even on the third.
  3. Random Variable NN: Counts the number of even rolls in each outcome.
    • Example: For "eoe," N=2N = 2 since there are two even numbers.
  4. Random Variable XX: Defined in terms of NN as: X=2N24N+3X = -2N^2 - 4N + 3
    • This equation determines the value of XX for each outcome.

Calculating Values of XX

Let's calculate NN and then XX for each outcome:

  1. Outcome: eee
    • N=3N = 3 (3 even rolls)
    • X=2(3)24(3)+3=1812+3=27+3=24X = -2(3)^2 - 4(3) + 3 = -18 - 12 + 3 = -27 + 3 = -24
  2. Outcome: oee
    • N=2N = 2
    • X=2(2)24(2)+3=88+3=16+3=13X = -2(2)^2 - 4(2) + 3 = -8 - 8 + 3 = -16 + 3 = -13
  3. Outcome: eoe
    • N=2N = 2
    • X=2(2)24(2)+3=88+3=16+3=13X = -2(2)^2 - 4(2) + 3 = -8 - 8 + 3 = -16 + 3 = -13
  4. Outcome: eoo
    • N=1N = 1
    • X=2(1)24(1)+3=24+3=3X = -2(1)^2 - 4(1) + 3 = -2 - 4 + 3 = -3
  5. Outcome: oeo
    • N=1N = 1
    • X=2(1)24(1)+3=24+3=3X = -2(1)^2 - 4(1) + 3 = -2 - 4 + 3 = -3
  6. Outcome: ooe
    • N=1N = 1
    • X=2(1)24(1)+3=24+3=3X = -2(1)^2 - 4(1) + 3 = -2 - 4 + 3 = -3
  7. Outcome: eoo
    • N=1N = 1
    • X=2(1)24(1)+3=24+3=3X = -2(1)^2 - 4(1) + 3 = -2 - 4 + 3 = -3

Probability Distribution of XX

To calculate the probability distribution, we need to consider:

  1. Total number of outcomes: There are 2×2×2=82 \times 2 \times 2 = 8 outcomes (since each roll can be either odd or even).
  2. Probability of each outcome: Since the die is fair, each outcome has a probability of 18\frac{1}{8}.

Now, let's tabulate the probability of each value of XX:

Value of XXOccurrencesProbability P(X=x)P(X = x)
-24118\frac{1}{8}
-13228=14\frac{2}{8} = \frac{1}{4}
-3558\frac{5}{8}

Final Answer

The probability distribution is:

  • P(X=24)=18P(X = -24) = \frac{1}{8}
  • P(X=13)=14P(X = -13) = \frac{1}{4}
  • P(X=3)=58P(X = -3) = \frac{5}{8}

Would you like a further breakdown or additional help on this problem?

Related Questions:

  1. What is the probability of having exactly one even roll?
  2. How does changing the random variable formula affect the probability distribution?
  3. What is the expectation value (mean) of XX?
  4. How many different outcomes are there if we consider NN alone?
  5. What is the variance of the random variable XX?

Tip: When solving probability problems, always count the total outcomes and ensure that the sum of probabilities equals 1.

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Math Problem Analysis

Mathematical Concepts

Probability Distribution
Discrete Random Variables
Combinatorics

Formulas

X = -2N^2 - 4N + 3
Probability of an event P(X = x) = (number of favorable outcomes / total outcomes)

Theorems

Fundamental Principle of Counting
Discrete Probability Distributions

Suitable Grade Level

Grades 10-12