A trend study focuses on:

A trend study is designed to observe how certain variables or phenomena change over a particular period. By focusing on changes over time, researchers can identify patterns, shifts, or developments within the data or subject matter being studied. This type of research is particularly useful for understanding long-term trends and societal changes, such as shifts in public opinion, behavior, or other measurable factors.

In contrast, while funding sources, statistical significance, and control groups are all important concepts in research methods, they do not encapsulate what a trend study specifically aims to investigate. Funding sources relate to the financial backing of research, statistical significance pertains to the reliability and validity of findings, and control groups are used in experimental designs to compare with treatment groups. These aspects do not inherently focus on the temporal changes that are the hallmark of a trend study.