Explain the below scenario 

A research project studied the physical properties of wood materials constructed by bonding together small flakes of wood. One of the questions of interest is the effect of the flake size and tree species on the tension modulus of elasticity in the direction perpendicular to the alignment of the flakes, in pounds per square inch (psi). This project considered two flake sizes, 0.15 inches by 2 inches and 0.25 inches by 2 inches, and three tree species: aspen, birch, and maple. For each combination of the flake size and tree species, three samples of wood material were constructed, and measure the tension modulus of elasticity.