Understanding Research Study Types

The question asks to identify the research study type where a researcher observes changes within a specific sub-population over a period. This requires tracking the same group longitudinally.

Analyzing Study Designs

• Trend Study: Examines changes within a general population over time, but not necessarily the same individuals or a specific, defined sub-group.
• Cohort Study: Follows a defined group (cohort) of individuals sharing a common characteristic (e.g., exposure, birth year) over time to observe outcomes and changes within that specific group. This directly matches the question's requirement to examine a 'specific sub-population' as they 'change time'.
• Cross-Sectional Study: Captures data from a population at a single point in time. It does not track changes over time.
• Panel Study: A type of longitudinal study that follows the exact same individuals over time, interviewing or observing them repeatedly. While similar to cohort studies, cohort studies focus on groups defined by a shared characteristic, making them the most fitting answer for observing changes in a 'specific sub-population' as described.

Identifying the Correct Study Type

Based on the analysis, a Cohort Study is the research design where a researcher examines specific sub-populations as they change over time.

Correct Answer: Option B (Cohort Study)