A Statistics Instructor Wishes to Know the Average Age (In

A Statistics instructor wishes to know the average age (in month) of his 200 students.He is too lazy to sample all 200 students so he decides to choose 20 students at random from the class and ask them for their age.He breaks the class up into two groups,males and females.He then selects a SRS of size 10 from each gender group.This sampling method is called a

A) Cluster Sample.
B) Simple Random Sample.
C) Voluntary Sample.
D) Stratified Random Sample.
E) Systematic Random Sample.