Question

Question 2. Which of the following describes stratified random sampling? Explain why it is correct and why it is incorrect

1. The first 95% of the people who respond to a mailed survey make up the sample, while the remaining 5% are not included because they constitute the 5% late-error-rate.

2. The first half of a volunteer sample that shows up is put in a group together-and the second half is grouped together. Thus, we are left with a sample with two sub groups (subgroups A and B).

3. Proportions of subgroups are chosen based on the fact that 60% of the population is right -handed and 40% is left handed. So 60% of the participants chosen are also left-handed and 40% of those chosen are right handed.

4. For a study on charter schools in Manhattan, a list of the Charter schools in the area is generated and participants are then randomly selected from each school (sub-group).

Answer 1

In stratified sampling plan, the population is divided in sub-groups where in every group is homogenous within itself and heterogeneous with respect to other groups.

The last example of study of charter schools in Manhattan is stratified sampling because firstly groups of charter schools in areas were formed and then samples were selected from each.

In the rest of the examples, homogenous groups were not formed. Groups were formed according to some different criteria. Thus they are not stratified sampling.