11.82 Plastics made under different environmental conditions are known to have differing strengths.

A scientist would like to know which combination of temperature and pressure yields a plastic with a high breaking strength. A small preliminary experiment was run at two pressure levels and two temperature levels. The following model was proposed:

where breaking strength (pounds)

temperature (F)

pressure (pounds per square inch)

A sample of observations yielded with sb N 1 = 1.11 sb N 2 = 0.27 sb N 3 = 0.34 yN = 226.8 + 4.9x1 + 1.2x2 - 0.7x1x2 n = 16 x2 =

x1 =

Y =

E(Y) = b0 + b1x1 + b2x2 + b3x1x2 a = 0.10 b5x1x2 x2 = 60, 75, and 90 yN a = 0.05 R2

+ b5x1x2 + e Y = b0 + b1x1 + b2x2 + b3x1 2 + b4x22 x2 = 60, 75, and 90 yN a = 0.05 R2 Y = b0 + b1x1 + b2x2 + e Do the data in table below indicate that there is an interaction between temperature and pressure?
Test by using .