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The mean value of 20 observations was found to be 75, but later on it was detected that 97 was misread as 79. Find the correct mean.
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- 75.7
- 75.8
- 75.9
- 75.6
- 75.7
Correct Option: C
Later on it was detected that 97 was misread as 79 .
Then ,Difference = 97 – 79 = 18
| True average = 75 + | |
| 20 |
True average = 75.9
Second method to solve this question with the help of given formula :
Here, n = 20, m = 75 , a = 97, b = 79
| Correct Average = m + | |
| n |
| Correct Average = 75 + | |
| 20 |
| Correct Average = 75 + | |
| 20 |
Correct Average = 75 + 0.9 = 75.9
