Question

The mean of 10 observations is 72. It was found that two observations 65 and 85 were misread as 56 and 58. Find the correct mean.

Answer 1

Given:

Number of observations = 10

Given mean = 72

Step-wise calculation:

1. Total   ...(Given) 

= Mean × Number

= 72 × 10

= 720

2. Sum of misread observations

= 56 + 58

= 114

3. Sum of correct observations

= 65 + 85

= 150

4. Corrected total

= 720 – 114 + 150

= 720 + 36

= 756 

5. Correct mean

= Corrected total ÷ Number

= 756 ÷ 10

= 75.6