Answer: 15.
- A 10
- B 12
- C 15
- D 20
Correct answer: C. 15
Explanation: Mean = (5+10+15+20+25)/5 = 75/5 = 15.
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