1. Protecting wood How can we help wood surfaces resist weathering, especially when restoring historic wooden buildings? In a study of this question, researchers prepared wooden panels and then exposed them to the
weather. Here are some of the variables recorded:

type of wood (yellow poplar, pine, cedar)

type of water repellent (solvent-based, water-based)

paint thickness (millimeters)

paint color (white, gray, light blue)
weathering time (months)

Identify each variable as categorical or quantitative.