Question

Arithmetic mean of nine observations is calculated as 38. But in doing so, an observation 27 is mistaken for 72. Find the actual mean of the data.

Answer 1

The mean of 9 observations = 38 

The sum of 9 observations = 38 × 9 = 342 

If the observation 27 is mistaken for 72 

then correct observation = 72 – 27 = 45 

Sum of correct observations = 342 + 45 = 387 

∴ Correct Mean = 387/9  = 43