What is assumed mean &how can we find it

how to use log & antilogtable to find square roots

What is the difference between mean deviation and standard deviation?

find dy/dx if y =(sec x+tanx )/(secx-tanx)

Find the mean and variance of the first n even natural numbers

 When do we use step-deviation method.Please explain the method.

the mean and standard deviation of 100 observations were calculated as 40 and 5.1 resp. by a student who took by mistake 50 instead of 40 for one observation. what are correct mean and standard deviation?

what is the meaning of discrete frequency distribution ?

The variance of 15 observations is 4.If each observation is increased by 9,find the variance of the resulting observations?

please give a detailed expalanation

let x₁, x₂, x₃,....... x_n be n values of a variable X. If these values are changed to x₁+a, x₂+a,.... x_n +a, where a belongs to R, show that the variance remains unchanged.

the mean of 5 observations is 4.4 and their variance is 8.24.if three of the observations are 1,2,6 .,find the other two observations.....

Find the mean deviation from the mean and standard deviation of the series:

a, a+d, a+2d, ....., (a+nd), .... a+(2n-1)d, a+2nd

its urgent..