Hello,
\($\sum_{i=1}^8 x_{i} =13*8=104\\$\)
\($\sum_{i=1}^7 x_{i} =11*7=77\\$\)
\(x_{8} =104-77=27\)
Var=7.71²=59.4441
\(m_{2} - m_{1} ^2=59.4441\\
m_{2} 59.4441+13^2=228.441\\\\
\sum_{i=1}^8x_i=228.4441*8=1827.5528\\\\
\sum_{i=1}^7x_i=1827.5528-27^2=1098.5528\\\\
m'_{2} - m'_{1} ^2= \frac{1098.5528}{7}-11^2=35.93611...\\\\
\sigma'= \sqrt{35.93611...} =5.994673...\)
