Question

Mean of 50 observations was found to be 80.4. But later on it was discovered that 96 was misread as 69 at one place.Fund the correct mean. If in each observations a constant value`kis added,how is the mean affected?

Answer 1

incorrect mean = (x1+x2--------x50)/50 

80.4 = (x1+x2--------x50)/50

80.4*50 = (x1+x2-------x50)

4020 = (x1+x2--------------x50)

the sum of the incorrect observation is 4020

if later it was discovered that 96 was misread as 69, then the correct sum of observations will 

4020+(96-69)

4020+ 27

= 4047

then the sum of correct 50 observations is 4047

then 

correct mean = (4047)/50

correct mean = 80.94

i hope this will help you 



- by ABHAY

Answer 2

mean = sum of observation /total no. of observation.
80=sum/50
sum=80*50
sum=4000
4000-69+96
4027=sum
mean =4027/50
80.54=mean
sum=(4027)k
now mean =(4027)k/50=80.54
(4027)k=80.54*50
(4027)k=4027
(k=1)
hope it helps!! :)