Alexander uses cupric chloride to etch circuit boards. He recorded the room temperature, in °C, and the um
etching rate, in of the cupric chloride.
min
After plotting his results, Alexander noticed that the relationship between the two variables was fairly
linear, so he used the data to calculate the following least squares regression equation for predicting the
etching rate from the room temperature:
1
9 =21
+
What is the residual if the room temperature was 25 C and the cupric chloride had an etching rate of
um
5 ?
min