Question

The mean of $100$ items was found to be $64.$ Later on, it was discovered that two items were misread as $26$ and $9$ instead of $36$ and$90$ respectively. Find the correct mean .

Answer 1

Mean $=$ sum of observations/number of observations

Given mean of $100$ items $=64$

Sum of observations $=6400$

Sum of misread items $=26+9=35$

Sum of actual items $=36+90=126$

So correct sum=$6400-35+126$

$=6491$

Correct mean $=\frac{6491}{100}$

$=64.91$