Question
Times Spent in Rush-Hour Traffic A sample of 9 drivers shows the time that they spent (in minutes) stopped in rushhour traffic on a specific snowy day last winter. Round your answers to one decimal place. \[ \begin{array}{lllllllll} 52 & 71 & 63 & 58 & 70 & 47 & 65 & 54 & 56 \end{array} \] Send data to Excel Part 1 of 3 Find the range. The range is \( \square \) 24.0 Alternate Answer: The range is 24 . Part: \( 1 / 3 \) Part 2 of 3 Find the variance. The variance is \( \square \) .
Ask by Garrett Deleon. in the United States
Jan 23,2025
Real Tutor Solution
Tutor-Verified Answer
Answer
The variance is 67.8.
Solution
To find the **variance** of the time spent by the 9 drivers in rush-hour traffic, follow these steps:
### Step 1: Calculate the Mean
First, determine the average (mean) time.
\[
\text{Mean} = \frac{52 + 71 + 63 + 58 + 70 + 47 + 65 + 54 + 56}{9} = \frac{536}{9} \approx 59.6 \text{ minutes}
\]
### Step 2: Calculate Each Deviation from the Mean and Square It
Next, subtract the mean from each data point and square the result:
\[
\begin{align*}
(52 - 59.6)^2 &\approx (-7.6)^2 = 57.8 \\
(71 - 59.6)^2 &\approx (11.4)^2 = 129.96 \\
(63 - 59.6)^2 &\approx (3.4)^2 = 11.56 \\
(58 - 59.6)^2 &\approx (-1.6)^2 = 2.56 \\
(70 - 59.6)^2 &\approx (10.4)^2 = 108.16 \\
(47 - 59.6)^2 &\approx (-12.6)^2 = 158.76 \\
(65 - 59.6)^2 &\approx (5.4)^2 = 29.16 \\
(54 - 59.6)^2 &\approx (-5.6)^2 = 31.36 \\
(56 - 59.6)^2 &\approx (-3.6)^2 = 12.96 \\
\end{align*}
\]
### Step 3: Sum the Squared Deviations
\[
57.8 + 129.96 + 11.56 + 2.56 + 108.16 + 158.76 + 29.16 + 31.36 + 12.96 = 542.48
\]
### Step 4: Calculate the Variance
Since this is a sample of drivers, we'll use the **sample variance** formula:
\[
\text{Variance} = \frac{\sum (\text{deviations}^2)}{n - 1} = \frac{542.48}{9 - 1} = \frac{542.48}{8} \approx 67.8
\]
### **Final Answer:**
The variance is **67.8**.
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Mind Expander
To find the range, you subtract the smallest value from the largest value in your data set. In your case, the largest time spent in rush-hour traffic is 71 minutes, and the smallest is 47 minutes. So, the range is \( 71 - 47 = 24 \) minutes. For variance, the formula is the average of the squared differences from the mean. First, calculate the mean of your data set, then find the squared differences for each value, average those squared differences, and voilà! Your variance will be revealed. Remember, variance helps understand how spread out the times are from the mean!