Alexander uses cupric chloride to etch circuit boards. He recorded the room temperature, in ^\circ\text{C}
∘
Cdegrees, start text, C, end text, and the etching rate, in \dfrac{\mu\text{m}}{\text{min}}
min
μm
​
start fraction, mu, start text, m, end text, divided by, start text, m, i, n, end text, end fraction, of the cupric chloride.
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:
\hat y = 2 +\dfrac{1}{5} x
y
^
​
=2+
5
1
​
xy, with, hat, on top, equals, 2, plus, start fraction, 1, divided by, 5, end fraction, x
What is the residual if the room temperature was 25^\circ\text{C}25
∘
C25, degrees, start text, C, end text and the cupric chloride had an etching rate of 5\dfrac{\mu\text{m}}{\text{min}}5
min
μm
​
5, start fraction, mu, start text, m, end text, divided by, start text, m, i, n, end text, end fraction ?
\dfrac{\mu\text{m}}{\text{min}}
min
μm
​