a)
Before plating the thickness of bracket for vendor 3 is the lowest, for the vendor to is mediocre, and for vendor one it is the highest.
As observed from the individual plot of thickness, it is clearly evident that for each vendor 1 2 and 3 the thickness of each
bracket after plating was decreased to a considerable amount as compared to before plating.
My covariate for this model is Y depicting after plating is held constant. My dependent variable is the thickness of the bracket. The independent variable is three types of vendors.
Holding the effect of X and Y constant, the individual values lot of thickness indicates that there is a difference in the thickness of bracket for vendor 1, 2 and 3
b)
ANCOVA
V=1; t = 91.25 - 50.00 y
V=2; t = 77.25 - 50.00 y
V=3; t = 67.50 - 50.00 y
General Linear Model: t versus y, v
Method
Factor coding (-1, 0, +1)
Factor Information
Factor Type Levels Values
v Fixed 3 1, 2, 3
Analysis of Variance
Source DF Adj SS Adj MS F-Value P-Value
y 1 15000.0 15000.0 36.72 0.000
v 2 2280.3 1140.2 2.79 0.085
Error 20 8169.0 408.4
Lack-of-Fit 2 156.0 78.0 0.18 0.841