If the mean of the set of numbers ${x_1}, {x_2}, {x_3}, ..., {x_n}$ is $\bar x$,then the mean of the numbers ${x_i} + 2i$,$1 \le i \le n$ is

The most stable measure of central tendency is

The median of a set of $19$ observations is $30$. If two observations with values $8$ and $32$ are added,what is the median of the new set of $21$ observations?

If the values $1, \frac{1}{2}, \frac{1}{3}, \frac{1}{4}, \frac{1}{5}, \dots, \frac{1}{n}$ occur at frequencies $1, 2, 3, 4, 5, \dots, n$ in a distribution,then the mean is

The mean of a set of observations is $\bar{x}$. If each observation is divided by $\alpha$ $(\alpha \neq 0)$ and then increased by $10$,what is the mean of the new set?

$A$ school has four sections of chemistry in class $XII$ having $40, 35, 45$ and $42$ students. The mean marks obtained in chemistry test are $50, 60, 55$ and $45$ respectively for the four sections. The overall average of marks per student is: