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For a group of 200 candidates, the average score was calculated as 40 and the standard deviation as 15. It was then noticed that one mark of 40 had been mistakenly taken as 50. What are the corrected mean and standard deviation, respectively?
- 14.98, 39.95
- 39.95, 14.98
- 39.95, 224.5
- None of these
Correct answer: 39.95, 14.98
Solution
The corrected mean is lower because the mistaken score was higher than the actual score, which reduces the average when corrected. The standard deviation also decreases slightly as the correction reduces the spread of the scores.
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