Question

The mean of 15 observations is 10. If 2 is subtracted from each observation. Find the new mean?

Answer 1

Let the 15 observations be X1,X,X3,X4.......,X15
Mean of 15 observations= X1+X2+X3+X4+.....X15/15
10 = X1+X2+X3+X4+......X15/15
X1+X2+X3+X4+.........X15= 150
A/Q,
2 is subtracted from observations New observations = X1-2,X2-2,X3-2,X4-2,.....X15-2
New mean = X1-2+X2-2+X3-2+X4-2......X15-2/15
= (X1+X2+X3+X4+......X15)-2/15
= 150-2/15 = 148/15 = 9.86

HENCE,
NEW MEAN = 9.86