Math Problem Statement

The number of dogs per household in a small town with probabilities for each number of dogs. Find the mean, variance, and standard deviation of the probability distribution.

Solution

To solve this problem, let's go through each part.

Given Data:

The table shows the number of dogs per household in a small town along with their corresponding probabilities:

Dogs (X)012345
Probability (P(X))0.6910.1950.0770.0190.0120.007

(a) Finding the Mean (μ) of the Probability Distribution

The mean (expected value) of a probability distribution can be calculated using the formula: μ=E(X)=XP(X)\mu = E(X) = \sum X \cdot P(X)

Let's calculate each term:

  1. 00.691=00 \cdot 0.691 = 0
  2. 10.195=0.1951 \cdot 0.195 = 0.195
  3. 20.077=0.1542 \cdot 0.077 = 0.154
  4. 30.019=0.0573 \cdot 0.019 = 0.057
  5. 40.012=0.0484 \cdot 0.012 = 0.048
  6. 50.007=0.0355 \cdot 0.007 = 0.035

Now, summing these results: μ=0+0.195+0.154+0.057+0.048+0.035=0.489\mu = 0 + 0.195 + 0.154 + 0.057 + 0.048 + 0.035 = 0.489

So, the mean (μ) is approximately 0.5 when rounded to one decimal place.

(b) Finding the Variance (σ²) and Standard Deviation (σ) of the Probability Distribution

The variance of a probability distribution is calculated as: σ2=E(X2)μ2\sigma^2 = E(X^2) - \mu^2 where E(X2)=X2P(X)E(X^2) = \sum X^2 \cdot P(X).

Let's calculate E(X2)E(X^2):

  1. 020.691=00^2 \cdot 0.691 = 0
  2. 120.195=0.1951^2 \cdot 0.195 = 0.195
  3. 220.077=0.3082^2 \cdot 0.077 = 0.308
  4. 320.019=0.1713^2 \cdot 0.019 = 0.171
  5. 420.012=0.1924^2 \cdot 0.012 = 0.192
  6. 520.007=0.1755^2 \cdot 0.007 = 0.175

Summing these: E(X2)=0+0.195+0.308+0.171+0.192+0.175=1.041E(X^2) = 0 + 0.195 + 0.308 + 0.171 + 0.192 + 0.175 = 1.041

Now, we can find the variance: σ2=E(X2)μ2=1.041(0.5)2=1.0410.25=0.791\sigma^2 = E(X^2) - \mu^2 = 1.041 - (0.5)^2 = 1.041 - 0.25 = 0.791

The standard deviation (σ) is the square root of the variance: σ=0.7910.89\sigma = \sqrt{0.791} \approx 0.89

Summary of Answers:

  • Mean (μ) ≈ 0.5
  • Variance (σ²) ≈ 0.79
  • Standard Deviation (σ) ≈ 0.89

Would you like further clarification on any steps?


Here are five additional questions to help deepen your understanding:

  1. What would happen to the mean if a higher probability was assigned to larger numbers of dogs?
  2. How would you calculate the expected number of households with exactly two dogs?
  3. How does variance help in understanding the spread of dog ownership in households?
  4. What is the probability of having at least two dogs in a household?
  5. How would the standard deviation change if there were more households with 0 dogs?

Tip: Remember that the mean in a probability distribution is the "center" of the distribution, while the variance and standard deviation tell us how spread out the values are around this center.

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Math Problem Analysis

Mathematical Concepts

Probability Distribution
Expected Value
Variance
Standard Deviation

Formulas

Mean (μ) formula: μ = Σ(X * P(X))
Variance (σ²) formula: σ² = Σ(X² * P(X)) - μ²
Standard Deviation (σ) formula: σ = √(σ²)

Theorems

Expected Value Theorem
Variance Calculation for Probability Distribution

Suitable Grade Level

Grades 10-12