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Question
The mean of 12 observations is 45. It was found that two observations 38 and 52 were misread as 28 and 32. Find the correct mean.
Sum
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Solution
Given: The mean of 12 observations is 45. Two observations 38 and 52 were misread as 28 and 32.
Step-wise calculation:
1. Original (wrong) total
= Mean × Number
= 45 × 12
= 540
2. Sum of misread values
= 28 + 32
= 60
3. Sum of correct values
= 38 + 52
= 90
4. Adjustment
= Correct sum – Wrong sum
= 90 – 60
= 30
5. Correct total
= 540 + 30
= 570
6. Correct mean
= 570 ÷ 12
= 47.5
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