Question

If the mean of five observations x,x+2,x+4,x+6,x+8 is 11,find the mean of first three observations. answer =9. but how?

Answer 1

Follow the steps First take the mean of five obs. (x +x+2+x+4+x+6+x+8)/5=11 5x + 20 = 11×5 5x +20 = 55 5x = 55 - 20 5x = 35 x = 7 By doing this we got the value of x. Now take the first 3 obs. x+x+2+x+4 (take the value of x and take out the mean) That will be (7+9+11)/3 = 27/3 = 9