Answer: Minimum and maximum values (or 1.5×IQR from Q1/Q3).
- A Mean plus or minus two standard deviations
- B Minimum and maximum values (or 1.5×IQR from Q1/Q3)
- C Exactly the first and third quartiles, Q1 and Q3
- D Mean plus or minus one standard deviation
Correct answer: B. Minimum and maximum values (or 1.5×IQR from Q1/Q3)
Explanation: Box-plot whiskers: conventionally extend to min/max values within 1.5 × IQR from Q1 and Q3. Points beyond are outliers.
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