Math Problem Statement

Consider a transmission system where the input, X, equals 1, 2, 3 or 4, with respective probabilities 0.1,

0.2, 0.4 and 0.3. The transmission system is imperfect. Given X = x, the output, Y, equals x or x +1, with

respective probabilities 0.7 and 0.3, when x is even. On the other hand, given X = x, the output, Y, equals

x or x –1, with respective probabilities 0.8 and 0.2, when x is odd. The system also has a feature that

reports an outcome, Z, which equals 0, 1 or 2, according as Y = X, Y > X or Y < X, respectively.

  1. The value of E(Z) is nearest to

A) 0.33 B) 0.34 C) 0.35 D) 0.36 E) 0.37

explain very simply, step by step, im very stupid

Solution

Let's break down the problem step by step. We need to find the expected value E(Z)E(Z), where ZZ is a variable that takes values 0, 1, or 2 depending on the relationship between YY and XX:

  • Z=0Z = 0 if Y=XY = X
  • Z=1Z = 1 if Y>XY > X
  • Z=2Z = 2 if Y<XY < X

Step 1: Understand the probabilities for XX

The input XX can be 1, 2, 3, or 4 with these probabilities:

  • P(X=1)=0.1P(X = 1) = 0.1
  • P(X=2)=0.2P(X = 2) = 0.2
  • P(X=3)=0.4P(X = 3) = 0.4
  • P(X=4)=0.3P(X = 4) = 0.3

Step 2: Determine the behavior of YY

The output YY depends on whether XX is even or odd:

  • If XX is even (2 or 4):
    • Y=XY = X with probability 0.7
    • Y=X+1Y = X + 1 with probability 0.3
  • If XX is odd (1 or 3):
    • Y=XY = X with probability 0.8
    • Y=X1Y = X - 1 with probability 0.2

Step 3: Calculate the probabilities for Z=0,1,2Z = 0, 1, 2

We calculate P(Z=0)P(Z = 0), P(Z=1)P(Z = 1), and P(Z=2)P(Z = 2) for each XX:

  1. For X=1X = 1 (odd):

    • Y=1Y = 1 (same as XX): Probability 0.8 → Z=0Z = 0
    • Y=0Y = 0 (less than XX): Probability 0.2 → Z=2Z = 2
  2. For X=2X = 2 (even):

    • Y=2Y = 2 (same as XX): Probability 0.7 → Z=0Z = 0
    • Y=3Y = 3 (greater than XX): Probability 0.3 → Z=1Z = 1
  3. For X=3X = 3 (odd):

    • Y=3Y = 3 (same as XX): Probability 0.8 → Z=0Z = 0
    • Y=2Y = 2 (less than XX): Probability 0.2 → Z=2Z = 2
  4. For X=4X = 4 (even):

    • Y=4Y = 4 (same as XX): Probability 0.7 → Z=0Z = 0
    • Y=5Y = 5 (greater than XX): Probability 0.3 → Z=1Z = 1

Step 4: Combine probabilities for Z=0,1,2Z = 0, 1, 2

Let's calculate the overall probabilities:

  • P(Z=0)=(0.1×0.8)+(0.2×0.7)+(0.4×0.8)+(0.3×0.7)P(Z = 0) = (0.1 \times 0.8) + (0.2 \times 0.7) + (0.4 \times 0.8) + (0.3 \times 0.7)
  • P(Z=1)=(0.2×0.3)+(0.3×0.3)P(Z = 1) = (0.2 \times 0.3) + (0.3 \times 0.3)
  • P(Z=2)=(0.1×0.2)+(0.4×0.2)P(Z = 2) = (0.1 \times 0.2) + (0.4 \times 0.2)

Simplifying:

  • P(Z=0)=0.08+0.14+0.32+0.21=0.75P(Z = 0) = 0.08 + 0.14 + 0.32 + 0.21 = 0.75
  • P(Z=1)=0.06+0.09=0.15P(Z = 1) = 0.06 + 0.09 = 0.15
  • P(Z=2)=0.02+0.08=0.10P(Z = 2) = 0.02 + 0.08 = 0.10

Step 5: Calculate E(Z)E(Z)

The expected value E(Z)E(Z) is:

E(Z)=0×P(Z=0)+1×P(Z=1)+2×P(Z=2)E(Z) = 0 \times P(Z = 0) + 1 \times P(Z = 1) + 2 \times P(Z = 2)

Substitute the probabilities:

E(Z)=0×0.75+1×0.15+2×0.10=0+0.15+0.20=0.35E(Z) = 0 \times 0.75 + 1 \times 0.15 + 2 \times 0.10 = 0 + 0.15 + 0.20 = 0.35

So, the expected value E(Z)E(Z) is closest to 0.35.

Answer:

The value of E(Z)E(Z) is nearest to C) 0.35.


Would you like more details or have any questions? Here are some follow-up questions:

  1. How do we calculate the variance of ZZ based on the given probabilities?
  2. What would happen if the probabilities for XX were different?
  3. Can you explain the concept of expected value in more detail?
  4. How do conditional probabilities apply to this problem?
  5. How would the solution change if the transmission system were perfect?

Tip: Always double-check your calculations, especially in problems with multiple steps involving probabilities.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Probability
Expected Value
Conditional Probability

Formulas

Expected Value Formula: E(X) = Σ [x * P(x)]
Conditional Probability: P(A|B) = P(A ∩ B) / P(B)

Theorems

Law of Total Probability

Suitable Grade Level

Grades 11-12