Answer:
Ruby was conducting a comparative investigation.
Step-by-step explanation:
There are three types of investigations: comparative, experimental, and descriptive. The comparative investigation involves collecting data (observations or measures) without controlling the independent variables. Therefore, you cannot be sure of the effects of different variables. On the other hand, in experimental investigations, you can be sure about the effects of the different variables by designing an experiment where you controlled them individually and joined. Finally, descriptives investigation, as the name says, consists of describing observations and patterns.