Statistics and Probability Lesson 3: Mean, Variance, SD of Discrete Probability Distribution

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Questions and Answers

What does the mean of a discrete random variable represent?

  • The spread of the distribution
  • The probability of each value
  • The sum of all values
  • The weighted average of possible values (correct)

In finding the mean of a discrete probability distribution, what is the first step?

  • Calculate the sum of X * P(X)
  • Subtract the computed mean from each value
  • Construct the probability distribution (correct)
  • Determine the value of X * P(X)

What does the variance of a discrete random variable measure?

  • The spread of the distribution
  • The probability of the random variable
  • The variability of the distribution (correct)
  • The sum of all values

Which step is involved in finding the variance of a discrete probability distribution?

<p>Multiply each (X - mean)² by its corresponding probability (A)</p> Signup and view all the answers

What does ∑(X - 𝝁)² * P(X) represent in the variance formula of a discrete probability distribution?

<p>The sum of squared differences between values and mean (B)</p> Signup and view all the answers

When finding the mean, what is multiplied by the corresponding probabilities?

<p>(X - mean) (C)</p> Signup and view all the answers

What is the formula for calculating the standard deviation of a probability distribution?

<p>√∑(𝑿 − 𝝁)𝟐 ∙ 𝑷(𝑿) (B)</p> Signup and view all the answers

What is the purpose of Step 3 in finding the mean, variance, and standard deviation of a probability distribution?

<p>Finding the mean of the expected value (C)</p> Signup and view all the answers

In Step 6 of calculating the probability distribution, what operation is performed on each result obtained in Step 5?

<p>Multiplying (B)</p> Signup and view all the answers

What is Step 8 primarily responsible for in the process of finding the standard deviation?

<p>Finding the square root of the variance (B)</p> Signup and view all the answers

If 𝝈 = 0.866, what does this value represent in relation to the probability distribution?

<p>Standard Deviation (A)</p> Signup and view all the answers

What does the standard deviation of a random variable measure?

<p>The average distance from the mean (B)</p> Signup and view all the answers

In the context of a discrete probability distribution, what does 𝜇 represent?

<p>Mean (C)</p> Signup and view all the answers

How is the variance calculated for a discrete random variable in this context?

<p>By multiplying each value by its corresponding probability and summing the results (A)</p> Signup and view all the answers

What is the formula to calculate the standard deviation for a discrete probability distribution?

<p>∑(𝑿 − 𝝁)𝟐 ∙ 𝑷(𝑿) (D)</p> Signup and view all the answers

What does Step 7 in the process entail when calculating the variance?

<p>Summing the results obtained in Step 6 (D)</p> Signup and view all the answers

How can the standard deviation be obtained from the variance value?

<p>Take the square root of the variance (D)</p> Signup and view all the answers

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Study Notes

Mean of a Discrete Probability Distribution

  • The mean of a discrete random variable X is a weighted average of the possible values that the random variable can take.
  • Formula: 𝝁 = ∑ 𝑿 ∙ 𝑷(𝑿)
  • Steps to find the mean:
    • Construct the probability distribution for the random variable.
    • Determine the value of 𝑿 ∙ 𝑷(𝑿)
    • Add all the values of to 𝑿 ∙ 𝑷(𝑿) to determine ∑ 𝑿 ∙ 𝑷(𝑿)

Variance of a Discrete Probability Distribution

  • The variance of a discrete random variable X measures the spread, or variability, of the distribution.
  • Formula: 𝝈𝟐 = ∑(𝑿 − 𝝁)𝟐 ∙ 𝑷(𝑿)
  • Steps to find the variance:
    • Subtract the computed mean from each value of the random variable: 𝑿 − 𝝁
    • Square the value obtained: (𝑿 − 𝝁)𝟐
    • Multiply the value obtained by the given probability: (𝑿 − 𝝁)𝟐 ∙ 𝑷(𝑿)
    • Find the variance by adding all products obtained

Standard Deviation of a Discrete Probability Distribution

  • The standard deviation of a random variable measures how close the random variable is to the mean.
  • Formula: 𝝈 = √∑(𝑿 − 𝝁)𝟐 ∙ 𝑷(𝑿)
  • Steps to find the standard deviation:
    • Find the variance: 𝝈𝟐 = ∑(𝑿 − 𝝁)𝟐 ∙ 𝑷(𝑿)
    • Take the square root of the variance: 𝝈 = √𝝈𝟐

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