Answer: 8.25.
- A 8.25
- B 9.5
- C 10
- D 7.5
Correct answer: A. 8.25
Explanation: Variance of first n natural numbers = (n² − 1)/12 = 99/12 = 8.25.
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