The given data set is,
44.4, 43.8 , 45.6, 45.9, 44.1, 45.6, 44.0, 44.9, 45.8.
a).
The mean can be determined as,
[tex]\begin{gathered} M=\frac{44.4+43.8+45.6+45.9+44.1+45.6+44.0+44.9+45.8}{9} \\ =\frac{404.1}{9} \\ =44.9 \end{gathered}[/tex]Thus, the required mean is 44.9 minutes.
b).
The MAD can be determined as,
[tex]\begin{gathered} \text{MAD}=\frac{1}{n}\Sigma\lvert x_i-M\rvert \\ =\frac{0.5+1.1+0.7+1.0+0.8+0.7+0.9+0+0.9}{9} \\ =\frac{6.6}{9} \\ =0.73 \end{gathered}[/tex]Thus, the required value of MAD is 0.73.