Question

plzz second one.....

Answer 1

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

Given that mean of four observations = 12.

x1 + x2 + x3 + x4/4 = 12.  ----- (1).


Given that first, second, third and 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! 

Answer 2

let the obs be a,b,c,d

mean = 12

a+b+c+d/4 = a - 1 + b - 2 + c - 3 + d - 4/4

a+b+c+d/4 - 10/4 = 12 - 2.5 = 9.5
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