Answer: 4.
- A 2
- B 3
- C 4
- D 5
Correct answer: C. 4
Explanation: Mean = 9. Deviations: 6, 3, 0, 3, 6. Mean deviation = (6+3+0+3+6)/5 = 18/5 = 3.6. Closest to 4.
In a perfectly normal (bell-shaped) distribution, mean, median, and mode all coincide at the centre; about 68% of data falls within 1 standard deviation of the mean, 95% within 2, and 99.7% within 3 - the empirical rule used to judge how typical or extreme a value is.
Concept context
Mean, median, mode, standard deviation, and data interpretation