The following data gives the information on the observed lifetimes (in hours) of 225 electrical components :

Modal class of the given data is 60-80.

Here, $\ell=60, \mathrm{f}_{\mathrm{m}}=61, \mathrm{f}_{1}=52, \mathrm{f}_{2}=38$ and $\mathrm{h}=20$.

Mode $=\ell+\left\{\frac{\mathbf{f}_{\mathbf{m}}-\mathbf{f}}{\mathbf{2 f}_{\mathbf{m}}-\mathbf{f}_{\mathbf{1}}-\mathbf{f}_{\mathbf{2}}}\right\} \times \mathbf{h}$

$=60+\left\{\frac{61-52}{122-52-38}\right\} \times 20$

$=60+\frac{\mathbf{9} \times \mathbf{2 0}}{\mathbf{3 2}}=60+\frac{\mathbf{4 5}}{\mathbf{8}}$

$=60+5.625$

$=65.625$ hours