Answer
$s_{b_1}=0.2166$
Work Step by Step
$s_e=229.547$ (item (b))
To find $s_x$:
In MINITAB, enter the Square Footage values in C1.
Select Stat -> Basic Statistics -> Display Descriptive Statistics
In Variables enter C1 and click in Statistics.
Select "Standard deviation". Click OK.
Click Ok.
$s_x=335.194$
$s_{b_1}=\frac{s_e}{\sqrt {∑(x_i-x ̅)^2}}=\frac{s_e}{\sqrt {n-1}s_x}$ (see note on page 684)
$s_{b_1}=\frac{229.547}{\sqrt {11-1}\times335.19}=0.2166$
