In a group of students,the mean weight of boys is $65 \ kg$ and the mean weight of girls is $55 \ kg$. If the mean weight of all students is $61 \ kg$,what is the ratio of the number of boys to the number of girls in the group?

The class marks of a distribution are $6, 10, 14, 18, 22, 26, 30$. The class size is:

$\bar{x}$ and $\bar{y}$ are the arithmetic means of the runs of two batsmen $A$ and $B$ in $10$ innings respectively,and $\sigma_{A}$ and $\sigma_{B}$ are the standard deviations of their runs. If batsman $A$ is more consistent than $B$,then he is also a higher run scorer only when

Let the mean and variance of $8$ numbers $-10, -7, -1, x, y, 9, 2, 16$ be $\frac{7}{2}$ and $\frac{293}{4}$ respectively. Then the mean of $4$ numbers $x, y, x + y + 1, |x - y|$ is:

Let $n \geq 3$. $A$ list of numbers $0 < x_1 < x_2 < \ldots < x_n$ has mean $\mu$ and standard deviation $\sigma$. $A$ new list of numbers is formed as follows: $y_1=0, y_2=x_2, \ldots, y_{n-1}=x_{n-1}, y_n=x_1+x_n$. The mean and the standard deviation of the new list are $\hat{\mu}$ and $\hat{\sigma}$. Which of the following is necessarily true?

$A$ factory is operating in two shifts,day and night,with $70$ and $30$ workers respectively. If the per day mean wage of the day shift workers is $Rs. 54$ and the per day mean wage of all the workers is $Rs. 60$,then the per day mean wage of the night shift workers (in $Rs.$) is: