The standard deviation of n observations `x_(1),x_(2),......,x_(n)` is 2. If `sum_(i=1)^(n)x_(i)=20` and `sum_(i=1)^(n)x_(i)^(2)=100` then n is

If sum_(i=1)^(n)sin x_(i)=n then sum_(i=1)^(n)cot x_(i)=

If sum_(i=1)^(n)sin x_(i)=n then sum_(i=1)^(n)cot x_(i)=

If sum_(i=1)^(n)(x_(i)-2)=110, sum_(i=1)^(n)(x_(i)-5)=20 , then what is the mean?

In a group of data, there are n observations, x,x_(2), ..., x_(n)." If "sum_(i=1)^(n)(x_(i)+1)^(2)=9n and sum_(i=1)^(n)(x_(i)-1)^(2)=5n , the standard deviation of the data is

If sum_(i=1)^(2n)cos^(-1)x_(i)=0 , then sum_(i=1)^(2n)x_(i) is :

A data consists of n observations : x_(1), x_(2),……, x_(n) . If Sigma_(i=1)^(n)(x_(i)+1)^(2)=11n and Sigma_(i=1)^(n)(x_(i)-1)^(2)=7n , then the variance of this data is

The mean deviation for n observations x_(1),x_(2),.........,x_(n) from their mean X is given by (a)sum_(i=1)^(n)(x_(i)-X)(b)(1)/(n)sum_(i=1)^(n)(x_(i)-X)(c)sum_(i=1)^(n)(x_(i)-X)^(2)(c)(1)/(n)sum_(i=1)^(n)(x_(i)-X)^(2)

sum_(i=1)^(n) sum_(i=1)^(n) i is equal to