Question

The mean of 10 observations was calculated as 40. It was detected on rechecking that the value of 45 was wrongly copied as 15 . Find the correct mean

Answer 1

Let terms be x1,x2,x3....................x10
Where x10 is taken 15 wrongly

so, x1+x2+...................x9+15/10= 40
      so, x1+x2+..............................x9 = 400-15 =385 ...............(1)


So original mean = x1+x2+.................x9+45/10
                         By Eqn (1)

                     Original Mean = 385+45/10
                                            = 430/10 
                                            = 43

So, Original Mean is 43.