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.