The efficiency for a steel specimen immersed in a phosphating tank is the weight of the phosphate coating divided by the metal loss (both in mg/ft2). An article gave the accompanying data on tank temperature (x) and efficiency ratio (y). Temp. 173 175 176 177 177 178 179 180
Ratio 0.88 1.37 1.32 1.07 1.11 1.00 0.96 1.88
Temp. 183 183 183 183 183 184 184 185
Ratio 1.37 1.58 1.71 2.15 2.23 0.80 1.47 0.92
Temp. 185 185 185 187 187 188 189 191
Ratio 1.89 1.96 2.70 1.41 2.48 3.06 1.89 3.14
(a) Determine the equation of the estimated regression line.
(b) Calculate a point estimate for true average efficiency ratio when tank temperature is 182.
(c) Calculate the values of the residuals from the least squares line for the four observations for which temperature is 182.