Answer
Mean:
$y ̅ =-12.4~mm~HG$
Standard deviation:
$y ̃=17.6~mm~HG$
Work Step by Step
$y ̅ =\frac{∑y_i}{n}=\frac{1.45+1.19+1.05+1.07}{4}=\frac{4.76}{4}=-12.4$
$s=\sqrt {\frac{∑(y_i-y ̅ )^2}{n-1}}=\sqrt {\frac{(-13-12.4)^2+(-13-12.4)^2+(-13-12.4)^2+(-13-12.4)^2+(-13-12.4)^2+(-13-12.4)^2+(-13-12.4)^2+(-13-12.4)^2+(-13-12.4)^2+(-13-12.4)^2}{10-1}}=17.59$
