The Mixed Arithmetic- Perceptual (MA-P) model is a componential model of graphic interaction that was developed based on analyses of humans interacting with graphical displays on the computer. The assumptions of the MA-P model were tested in a research article reported in the SIGCHI Bulletin (July 1993). Using simple linear regression, the researcher modeled response time y (in milliseconds) in a standard graph problem as a function of the number x of processing steps required to solve the problem. A summary of the regression results for n = 8 problems follows:

ŷ = 1,346 + 450x,   r² = .91

a. Interpret the value of β̂₁.

b. Interpret the value of r².

c. Conduct a test of model adequacy at α = .01.