Final answer:
An observation schedule is a tool used in structured observation to categorize behaviors systematically to facilitate consistent and reproducible data collection and reduce observer bias.
Step-by-step explanation:
The question, 'What is an observation schedule?' relates most closely to option (a) 'A set of explicit rules for assigning behaviour to categories.' This is because an observation schedule is a tool used in structured observation within research, such as sociological studies or psychological experiments, which requires researchers to systematically categorize and record behaviors according to predefined criteria. The aim is to facilitate the collection of consistent and reproducible data. For example, in observational research like the Strange Situation by Mary Ainsworth, infants' behaviors are monitored according to a specific observation schedule to assess attachment styles with their caregivers. It's essential for reducing observer bias, as it provides clear guidelines on what to observe and how to classify those observations.
An observation schedule also plays a role in ensuring inter-rater reliability, which is a measure of consistency among different observers' recordings. It's distinct from a timetable, a list of interview questions, or a measure of validity. Instead, it's part of the operational definition in research, which enables researchers to gather data in an empirical and systematic way.