Identify the sampling techniquesused, and discuss potential sources of bias(if any). Explain.

After a tornado,a disaster area is divided into 250 equal grids. Twenty of the grids are selected, and every occupied household in the grid is interviewed to help focus relief efforts on what residents require the most.What type of sampling is used?

A.

Stratified sampling isused, since the disaster area is divided intogrids, and some of those grids are selected and everyone in those grids is interviewed.

B.

Cluster sampling isused, since the disaster area is divided intogrids, and some of those grids are selected and everyone in those grids is interviewed.

C.

Cluster sampling isused, since the disaster area is divded intogrids, and a random sample is taken from each grid.

D.

Stratified sampling isused, since the disaster area is divded intogrids, and a random sample is taken from each grid.

What potential sources of bias are present, if any? Select all that apply.

A.

Certain grids may have been much more severely damaged than others. Severely damaged grids may have fewer occupied households.

B.

The sample only consists of grids that are easy to get. These grids may not be representative of the population.

C.

Certain grids may have been much more severely damaged than others. The grids that are selected may not be representative in terms of damage.

D.

There are no potential sources of bias.