Question

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

• A. 43
• B. 34
• C. 40
• D. 60

Answer 1

Answer:

A. 43

Solution:

Concept use:

Mean = Sum of the observation$\div$Total No of Observation.

Calculations:

The original sum of the numbers was 10 $\times$ 40 = 400 (since mean is the sum of the observations divided by the number of observations).

In the recheck, it was found that the number 45 was mistaken for 15, suggesting a difference of 45 - 15 = 30.

So, we add the difference to the original sum: 400 + 30 = 430.

Now, the correct mean is the adjusted sum divided by the number of observations: $\frac{430}{10} = 43.$

So, the correct mean is: 43