Answer: Proportional representation from each subgroup (stratum).
- A Every individual in the population has an exactly equal chance
- B Proportional representation from each subgroup (stratum)
- C Only random selection, with strata playing no role at all
- D Equal sample size drawn from every group, regardless of its size
Correct answer: B. Proportional representation from each subgroup (stratum)
Explanation: Stratified sampling: population divided into strata, samples taken from each stratum proportionally or as needed. Ensures representation.
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