The mean of 20 observations was found to be 45. It was later found that one observation, 64, had been wrongly copied as 46. What is the correct mean?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 45.9
Find the sum that was used, take out the wrong value and put in the right value, then divide by the number of observations again.
Sum used \(=20\times45=900\)
Correct sum \(=900-46+64=918\)
Correct mean \(\displaystyle=\frac{918}{20}=45.9\)