Math Problem Statement

Use the Sample Variance Definition to find the variance and standard deviation of the data. Round the answers to one decimal place. 3, 7, 4, 1, 10, 5

Solution

To solve the problem, let's calculate the sample variance and sample standard deviation for the given dataset [3,7,4,1,10,5][3, 7, 4, 1, 10, 5]. Here's the step-by-step solution:

1. Formula for Sample Variance

The sample variance s2s^2 is calculated as: s2=(xixˉ)2n1s^2 = \frac{\sum (x_i - \bar{x})^2}{n - 1} where:

  • xix_i are the data points,
  • xˉ\bar{x} is the sample mean,
  • nn is the number of data points.

2. Calculate the Mean (xˉ\bar{x})

xˉ=xin=3+7+4+1+10+56=306=5\bar{x} = \frac{\sum x_i}{n} = \frac{3 + 7 + 4 + 1 + 10 + 5}{6} = \frac{30}{6} = 5

3. Subtract the Mean and Square the Differences

For each data point, calculate (xixˉ)2(x_i - \bar{x})^2:

  • (35)2=(2)2=4(3 - 5)^2 = (-2)^2 = 4
  • (75)2=(2)2=4(7 - 5)^2 = (2)^2 = 4
  • (45)2=(1)2=1(4 - 5)^2 = (-1)^2 = 1
  • (15)2=(4)2=16(1 - 5)^2 = (-4)^2 = 16
  • (105)2=(5)2=25(10 - 5)^2 = (5)^2 = 25
  • (55)2=(0)2=0(5 - 5)^2 = (0)^2 = 0

4. Sum of Squared Differences

(xixˉ)2=4+4+1+16+25+0=50\sum (x_i - \bar{x})^2 = 4 + 4 + 1 + 16 + 25 + 0 = 50

5. Calculate the Variance

s2=(xixˉ)2n1=5061=505=10s^2 = \frac{\sum (x_i - \bar{x})^2}{n - 1} = \frac{50}{6 - 1} = \frac{50}{5} = 10

6. Calculate the Standard Deviation

The sample standard deviation ss is the square root of the variance: s=s2=103.2s = \sqrt{s^2} = \sqrt{10} \approx 3.2

Final Results:

  • Sample Variance: 10.010.0
  • Sample Standard Deviation: 3.23.2

Let me know if you would like more details or have additional questions!

Here are five related questions to deepen your understanding:

  1. How does sample variance differ from population variance?
  2. Why do we divide by n1n-1 instead of nn when calculating sample variance?
  3. Can you find the range of this dataset? How is it different from standard deviation?
  4. What would the variance be if all data points were identical?
  5. How is standard deviation useful in interpreting real-world data?

Tip: Always double-check calculations involving rounding when solving problems with specific decimal requirements.

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Math Problem Analysis

Mathematical Concepts

Statistics
Sample Variance
Standard Deviation

Formulas

Sample Variance: s^2 = Σ(x_i - x̄)^2 / (n - 1)
Standard Deviation: s = √(s^2)

Theorems

Definition of Variance and Standard Deviation

Suitable Grade Level

Grades 9-12