Topic: Engineering Mathematics
The arithmetic mean of 12 data point is 79. Later it was found that two data points were wrongly taken as 83 and 68 in place of 78 and 97. The actual mean is
- A. 79
- B. 75
- C. 81
- D. 77
Answer: C. 81
Explanation: Incorrect sum of the 12 data points $= 12 \times 79$. The difference between the correct values and incorrect values $= (78 + 97) - (83 + 68) = 175 - 151 = +24$. The correct sum is the incorrect sum plus 24. Thus, the new mean $= \frac{\text{Incorrect sum} + 24}{12} = 79 + \frac{24}{12} = 79 + 2 = 81$.