$F{E}_i=D_i-F_i$

RSFE$={\displaystyle \underset{i=1}{\overset{n}{}}}F{E}_i,$MFE$=\frac{{\displaystyle \underset{i=1}{\overset{n}{}}}F{E}_i}{n}=\frac{\text{R}\text{S}\text{F}\text{E}}{n}$

MSE$=\frac{{\displaystyle \underset{i=1}{\overset{n}{}}}(F{E}_i{)}^2}{n},$MAD$=\frac{{\displaystyle \underset{i=1}{\overset{n}{}}}|F{E}_i|}{n}$

MAPE$=\frac{100{\displaystyle \underset{i=1}{\overset{n}{}}}\frac{|F{E}_i|}{D_i}}{n},TS=\frac{{\displaystyle \underset{i=1}{\overset{n}{}}}F{E}_i}{\text{M}\text{A}\text{D}}=\frac{\text{R}\text{S}\text{F}\text{E}}{\text{M}\text{A}\text{D}}$

$-2\mathrm{.}000$

$-0\mathrm{.}667$

$0\mathrm{.}000$

$-1\mathrm{.}500$

$1\mathrm{.}333$

Question $21$