Question

The mean of 100 observations is 40. It is found that an observation 53 was misread as 83. the correct mean is

• A. $39.7$
• B. $39$
• C. $40$
• D. $39.5$

Answer 1

The correct option is A $39.7$

Mean of $100$ observations = $40$
Sum of $100$ observations = $40\times 100$ = $4000$
After replacing the misread observation $83$ to $53$,
Sum of $100$ observations = $4000-83+53$ = $3970$
New mean = $\frac{3970}{100}$ = $39.70$