The table shows the times, in minutes, that people waited: : people; : people; : people; : people. Estimate the mean waiting time.
Answer and explanation
Correct answer: C. 19 minutes
- Step 1: Use the midpoint of each class: .
- Step 2: Multiply by frequency and add: .
- Step 3: Divide by : minutes.
Answer
19 minutes.
Why not the others: 20 minutes: This averages the four midpoints without using the frequencies. 24 minutes: This uses the upper class boundaries instead of the midpoints. 15 minutes: This is the midpoint of the median class, not the estimated mean.
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