Math Problem Statement

Consider the discrete random variable X given in the table below. Calculate the mean, variance, and standard deviation of X.

Solution

Let's work through the calculations for variance σ2\sigma^2 using the information from the table.

Formula Recap:

For a discrete random variable XX with probabilities P(X)P(X), the variance σ2\sigma^2 is given by:

σ2=((xiμ)2P(X=xi))\sigma^2 = \sum \left( (x_i - \mu)^2 \cdot P(X = x_i) \right)

where:

  • xix_i are the values of XX,
  • P(X=xi)P(X = x_i) are the corresponding probabilities, and
  • μ\mu is the mean (which is given as μ=12.44\mu = 12.44).

Given Data:

The values of XX and their respective probabilities P(X)P(X) are: X:1,3,5,10,16,19,20X: 1, 3, 5, 10, 16, 19, 20 P(X):0.14,0.1,0.1,0.12,0.1,0.08,0.36P(X): 0.14, 0.1, 0.1, 0.12, 0.1, 0.08, 0.36

Step-by-Step Calculation:

  1. Subtract the mean μ=12.44\mu = 12.44 from each xix_i.
  2. Square the result of each subtraction.
  3. Multiply each squared result by the corresponding probability P(X)P(X).
  4. Sum all the results to get σ2\sigma^2.

Let me calculate that for you.The variance σ2\sigma^2 is approximately 58.7758.77.

If you have any further questions or want a detailed explanation, feel free to ask!

Here are five related questions you might find interesting:

  1. How is the standard deviation related to the variance?
  2. What is the significance of variance in statistics?
  3. Can you explain the difference between population variance and sample variance?
  4. How would the variance change if one of the probabilities increased or decreased?
  5. How does the shape of the probability distribution relate to the variance?

Tip: Variance gives you an idea of how spread out the values of a random variable are around the mean. The larger the variance, the more spread out the values.

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Math Problem Analysis

Mathematical Concepts

Probability
Discrete Random Variables
Mean
Variance
Standard Deviation

Formulas

Mean (μ) = Σ(x_i * P(X = x_i))
Variance (σ^2) = Σ((x_i - μ)^2 * P(X = x_i))
Standard Deviation (σ) = √(σ^2)

Theorems

Law of Total Expectation

Suitable Grade Level

Grades 10-12