Question

If the class interval are $10-19,20-29,30-39,.....$, then the upper limit of the first class interval will be

• A. $19$
• B. $19.5$
• C. $20$
• D. $20.5$

Answer 1

The correct option is B

$19.5$

Find the upper limit of the first class interval

Given, Class Intervals are $10-19,20-29,30-39,.....$

The given class Interval are not continuous, so, we have to make them continuous by finding the mean of the upper limit of first class and the lower limit of the second class.

To find the upper limit use the formula, $\frac{\mathrm{upper}\mathrm{limit}\mathrm{of}\mathrm{preceeding}\mathrm{limit}+\mathrm{lower}\mathrm{limit}\mathrm{of}\mathrm{succeeding}\mathrm{limit}}{2}$

Therefore, for the first class interval,

$$\begin{gathered} \mathrm{Mean}=\frac{19+20}{2} \\ =\frac{39}{2} \\ =19.5 \end{gathered}$$

Hence, $19.5$ is the upper limit of the first class interval

so $\mathrm{Option}\left(\mathrm{B}\right)$ is correct.