Answer
$s_e=0.368$
Work Step by Step
$ŷ =−0.0479x+69.0296$
$s_e=\sqrt {\frac{Σ(y_i-ŷ_i)^2}{n-2}}=\sqrt {\frac{[69.2-(−0.0479\times5+69.0296)]^2+[68.3−(-0.0479\times15+69.0296)]^2+[67.5−(-0.0479\times25+69.0296)]^2+[67.1−(-0.0479\times35+69.0296)]^2+[66.4−(-0.0479\times50+69.0296)]^2+[66.1−(-0.0479\times72+69.0296)]^2+[63.9-(−0.0479\times105+69.0296)]^2+}{7-2}}=0.368$
