Math Problem Statement

Each​ year, tornadoes that touch down are recorded. The following table gives the number of tornadoes that touched down during each month of one year. Determine the range and sample standard deviation. 4 2 52 114 198 95 66 86 72 60 103 92

Solution

To solve for the range and sample standard deviation, we will follow these steps:

Step 1: Calculate the Range

The range is the difference between the maximum and minimum values in the dataset.

  • Minimum value: 22
  • Maximum value: 198198

Range=1982=196\text{Range} = 198 - 2 = 196

Step 2: Calculate the Sample Standard Deviation

The formula for sample standard deviation (ss) is:

s=1n1i=1n(xixˉ)2s = \sqrt{\frac{1}{n-1} \sum_{i=1}^{n} (x_i - \bar{x})^2}

Where:

  • xix_i represents each data point,
  • xˉ\bar{x} is the sample mean,
  • nn is the sample size.

Step 2.1: Find the Mean

First, we calculate the mean (xˉ\bar{x}) of the dataTo solve for the range and sample standard deviation, we will follow these steps:

Step 1: Calculate the Range

The range is the difference between the maximum and minimum values in the dataset.

  • Minimum value: 22
  • Maximum value: 198198

Range=1982=196\text{Range} = 198 - 2 = 196

Step 2: Calculate the Sample Standard Deviation

The formula for sample standard deviation (ss) is:

s=1n1i=1n(xixˉ)2s = \sqrt{\frac{1}{n-1} \sum_{i=1}^{n} (x_i - \bar{x})^2}

Where:

  • xix_i represents each data point,
  • xˉ\bar{x} is the sample mean,
  • nn is the sample size.

Step 2.1: Find the Mean

First, we calculate the mean (xˉ\bar{x}) of the

xˉ=4+2+52+114+198+95+66+86+72+60+103+9212\bar{x} = \frac{4 + 2 + 52 + 114 + 198 + 95 + 66 + 86 + 72 + 60 + 103 + 92}{12}

Let's compute the mean:

xˉ=94412=78.67\bar{x} = \frac{944}{12} = 78.67

Step 2.2: Find the Squared Differences

Now, we calculate the squared differences between each data point and the mean:

(478.67)2=5585.35(4 - 78.67)^2 = 5585.35 (278.67)2=5886.35(2 - 78.67)^2 = 5886.35 (5278.67)2=711.89(52 - 78.67)^2 = 711.89 (11478.67)2=1210.89(114 - 78.67)^2 = 1210.89 (19878.67)2=14316.69(198 - 78.67)^2 = 14316.69 (9578.67)2=263.39(95 - 78.67)^2 = 263.39 (6678.67)2=163.39(66 - 78.67)^2 = 163.39 (8678.67)2=53.79(86 - 78.67)^2 = 53.79 (7278.67)2=44.49(72 - 78.67)^2 = 44.49 (6078.67)2=351.29(60 - 78.67)^2 = 351.29 (10378.67)2=589.69(103 - 78.67)^2 = 589.69 (9278.67)2=177.69(92 - 78.67)^2 = 177.69

Step 2.3: Compute the Sum of Squared Differences

Next, we sum these squared differences:

Sum=5585.35+5886.35+711.89+1210.89+14316.69+263.39+163.39+53.79+44.49+351.29+589.69+177.69\text{Sum} = 5585.35 + 5886.35 + 711.89 + 1210.89 + 14316.69 + 263.39 + 163.39 + 53.79 + 44.49 + 351.29 + 589.69 + 177.69 Sum=29054.9\text{Sum} = 29054.9

Step 2.4: Divide by n1n - 1

Since this is a sample, we divide by n1=121=11n - 1 = 12 - 1 = 11:

29054.911=2641.35\frac{29054.9}{11} = 2641.35

Step 2.5: Take the Square Root

Finally, we take the square root to find the sample standard deviation:

s=2641.3551.39s = \sqrt{2641.35} \approx 51.39

Final Answers:

  • Range: 196
  • Sample Standard Deviation: 51.39

Would you like more details or have any questions about these calculations?


Here are 5 relative questions that expand this information:

  1. How does the range affect the spread of the data?
  2. What is the difference between sample standard deviation and population standard deviation?
  3. How would the standard deviation change if the maximum value increased?
  4. Can you interpret what a high standard deviation means in this context?
  5. How does the sample size influence the accuracy of the standard deviation?

Tip: Always verify whether you're calculating the sample or population standard deviation, as this changes the divisor in the formula.

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Math Problem Analysis

Mathematical Concepts

Statistics
Descriptive Statistics
Range
Sample Standard Deviation

Formulas

Range = max(x) - min(x)
Sample Standard Deviation: s = sqrt((1/(n-1)) * Σ(x_i - x̄)^2)

Theorems

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Suitable Grade Level

Grades 10-12