Question

the mean of 20 observations is 15. on checking, it was found that two observations were wrongly copied as 3 and 6. if wrong observations are replaced by correct values 8 and 4, then the correct mean is

Answer 1

Mean of 20 observations = 15
Sum of 20 observations = (15×20) = 300

Sum of Two wrongly copied observations = (3+6) = 9

Sum of two correct observations = (4+8) = 12

Now according to the question,

Sum of the correct observations = ((300-9)+12) = 303

Mean of the correct observations = (303/20) = 15.15

Answer 2

Answer:

15

Step-by-step explanation:

Mean of 20 observations = 15

Sum of 20 observations = (15×20) = 300

Sum of Two wrongly copied observations = (3+6) = 9

Sum of two correct observations = (4+8) = 12

Now according to the question,

Sum of the correct observations = ((300-9)+12) = 303

Mean of the correct observations = (303/20) = 15.15