Answer
$μ=25.49~years$
$σ=5.44~years$
Work Step by Step
$x_1=First~Class~Midpoint=12.5$
$x_2=Second~Class~Midpoint=17.5$
$x_3=Third~Class~Midpoint=22.5$
$x_4=Fourth~Class~Midpoint=27.5$
$x_5=Fifth~Class~Midpoint=32.5$
$x_6=Sixth~Class~Midpoint=37.5$
$x_7=Seventh~Class~Midpoint=42.5$
$x_8=Eighth~Class~Midpoint=47.5$
$μ=\frac{Σx_if_i}{Σf_i}=\frac{12.5\times9.8+17.5\times551.9+22.5\times1226.4+27.5\times1108.2+32.5\times549.9+37.5\times140.7+42.5\times23.2+47.5\times1.1}{3611.2}=25.49$
$σ=\sqrt {\frac{(x_i-μ)^2f_i}{Σf_i}}=\sqrt {\frac{(12.5-25.49)^2\times9.8+(17.5-25.49)^2\times551.9+(22.5-25.49)^2\times1226.4+(27.5-25.49)^2\times1108.2+(32.5-25.49)^2\times549.9+(37.5-25.49)^2\times140.7+(42.5-25.49)^2\times23.2+(47.5-25.49)^2\times1.1}{3611.2}}=5.44$
