Which of the following refers to a sampling approach in structured observation whereby a sampled individual is observed for a set period of time?

The correct option is Focal sampling.

Step-by-step Explanation:

1. Understanding Focal Sampling:
In structured observation (often used in animal behavior studies, developmental psychology, and observational research), researchers require systematic strategies to record behavior accurately without bias. Focal sampling is a technique where a single specific individual (the "focal" subject) is selected and observed intensively for a predetermined, set period of time. During this observation window, the researcher records all behaviors and activities initiated or received by that focal individual. This provides a comprehensive and continuous record of a single subject's activities.

2. Why the Other Options are Incorrect:
• Snowball sampling: This is a non-probability sampling method used in survey research where initial study participants recruit future participants from their social networks. It is not an observational technique.
• Purposive sampling: Also known as judgmental sampling, this is a non-probability sampling method where the researcher selects participants based on their own judgment and the specific goals of the study. It does not dictate how an individual is observed over time.
• Cluster sampling: This is a probability sampling method where the researcher divides the population into separate groups (called clusters) and then randomly selects entire clusters to be part of the sample. It is a population sampling methodology rather than an observational recording technique.