Question

The mean of 10 observations is 42 If each observation in data is decreased by 12 What will be the new mean of data

Answer 1

sum of observations/no. of observations = mean
sum of 10 observations / 10 = 42

sum of 10 observations = 420

When each of the observation is reduced by 12, then

sum of new 10 observations = ( sum of original 10 observations ) - 12 * 10

= 420 - 120 = 300

new mean = 300/10 = 30