Answer
$s_e=0.9715$
Work Step by Step
$ŷ =0.2119x−0.31$
$s_e=\sqrt {\frac{Σ(y_i-ŷ_i)^2}{n-2}}=\sqrt {\frac{[20.0-(0.2119\times88.6−0.31)]^2+[19.8-(0.2119\times93.3−0.31)]^2+[17.1-(0.2119\times80.6−0.31)]^2+[14.7-(0.2119\times69.7−0.31)]^2+[15.4-(0.2119\times69.4−0.31)]^2+[15.0-(0.2119\times79.6−0.31)]^2+[16.0-(0.2119\times80.6−0.31)]^2+[14.4-(0.2119\times76.3−0.31)]^2+[16.0-(0.2119\times71.6−0.31)]^2+[18.4-(0.2119\times84.3−0.31)]^2+[15.5-(0.2119\times75.2−0.31)]^2+[17.1-(0.2119\times82.0−0.31)]^2+[16.2-(0.2119\times83.3−0.31)]^2+[17.2-(0.2119\times82.6−0.31)]^2+[17.0-(0.2119\times83.5−0.31)]^2}{15-2}}=0.9715$
