The marks distribution of $30$ students in a mathematics examination is given in the table. Find the mode of this data. Also,compare and interpret the mode and the mean.
Class interval$10-25$$25-40$$40-55$$55-70$$70-85$$85-100$
Number of students$2$$3$$7$$6$$6$$6$

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(52) To find the mean,we calculate the class marks $(x_i)$ and $f_i x_i$:
Class intervalNumber of students $(f_i)$Class mark $(x_i)$$f_i x_i$
$10-25$$2$$17.5$$35.0$
$25-40$$3$$32.5$$97.5$
$40-55$$7$$47.5$$332.5$
$55-70$$6$$62.5$$375.0$
$70-85$$6$$77.5$$465.0$
$85-100$$6$$92.5$$555.0$
Total$\Sigma f_i = 30$$\Sigma f_i x_i = 1860.0$

Mean $\bar{x} = \frac{\Sigma f_i x_i}{\Sigma f_i} = \frac{1860}{30} = 62$.
For the mode,the maximum frequency is $7$,which corresponds to the modal class $40-55$.
Here,$l = 40$,$h = 15$,$f_1 = 7$,$f_0 = 3$,$f_2 = 6$.
Mode $= l + \left( \frac{f_1 - f_0}{2f_1 - f_0 - f_2} \right) \times h = 40 + \left( \frac{7 - 3}{14 - 3 - 6} \right) \times 15 = 40 + \left( \frac{4}{5} \right) \times 15 = 40 + 12 = 52$.
Interpretation: The maximum number of students obtained $52$ marks (mode),while on average,a student obtained $62$ marks (mean).

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