Question

Mean of four observations is 12. if first, second,third and fourth observations are decreased by 1,2,3 and 4 respectively, then find the new mean.

Answer 1

Let the four observations be x1,x2,x3,x4.

Given that Mean of 4 observations = 12.

x1 + x2 + x3 + x4/4 = 12   ----------- (1)

Given that if 1st,2nd,3rd,4th observations are decreased by 1,2,3 and 4.

x1 - 1 + x2 - 2 + x3 - 3 + x4 - 4/4 

= x1 + x2 + x3 + x4 - 10/(4)

= x1 + x2 + x3 + x4/4 - 10/4

= 12 - 10/4

= 48 - 10/4

= 38/4

= 9.5.


Therefore the new mean = 9.5.


Hope this helps!