A frequency table shows class intervals of width 5: 10-14, 15-19, 20-24. What is the class mark (midpoint) of 15-19?
Answer and explanation
Correct answer: B. 17.0
- Step 1: The class mark is the midpoint between lower and upper limits. Step 2. Calculate: (15 + 19) / 2 = 34 / 2 = 17.0. Answer: 17.0. Why not the others: 16.5 uses boundaries incorrectly; 17.5 averages 15 and 20; 18.0 is an arithmetic error.
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