Answer to Question 1
Cluster sampling involves randomly selecting preexisting clusters or groups instead of randomly selecting individuals. The main advantages are (1) it is easy to obtain a large sample quickly, and (2) because the participants are already organized in groups, it is often easy and convenient to test them as a group. For example, you could hand out questionnaires to an entire class instead of giving questionnaires to one person at a time. The main concern with cluster sampling is that the individuals within a cluster may not be independent. If the clusters consist of families, for example, it is likely that all of the family members share some common interests and common experiences.
Answer to Question 2
b
Pulmonary function test: spirometry. (a) Normal respiratory volumes, as measured during spirometry.
Passive shoulder roll: mobilizing technique for the shoulder with recipient in supine position.
Scapula mobilizing technique: move and lift the scapula by pulling back at the shoulder.
viable surface sampling by swab
Gel electrophoresis, an essential laboratory technique in biological science research
A sampling of bacterial diversity. Most bacteria do not cause disease.