Answer: 35.
- A 30
- B 35
- C 40
- D 70
Correct answer: B. 35
Explanation: Class mark = (lower limit + upper limit)/2 = (30+40)/2 = 35.
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