Manufacturers Were Subdivided into Groups by Volume of Sales

Multiple Choice

Manufacturers were subdivided into groups by volume of sales. Those with more than $100 million in sales were classified as large; those from $50 to $100 million as medium size; and those between $25 and $50 million,and so on. Samples were then selected from each of these groups. What is this type of sampling called?

A) Simple random sampling
B) Stratified random sampling
C) Cluster sampling
D) Systematic sampling