Question

The mean of $20$ observations is $15.$ On checking it was found that the two observations were wrongly copied as $3$ and $6.$ The correct values are $8$ and $4$ , then correct mean will be given by:

• A. $15.15$
• B. $14.69$
• C. $14.74$
• D. $15.25$

Answer 1

The correct option is A $15.15$

Mean of 20 observatios $=15$

Sum of 20 observations $=15\times 20=300$

Correct sum $=300+8+4-3-6$

$=303$

Correct mean$=\frac{303}{20}=15.15$