Multiple choice

The mean of $8$ observations was found to be $20$. Later it was detected that one of the observations was misread as $62$. What is the correct observation, if the correct mean is $15.5$?

  1. $26$
  2. $28$
  3. $30$
  4. $29$
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A Correct answer
Explanation

Initial sum of 8 observations = 8 * 20 = 160. Correct sum = 8 * 15.5 = 124. The difference is 160 - 124 = 36. Subtracting this error from the misread value (62 - 36) gives the correct observation: 26.

AI explanation

The correct total sum of the 8 observations is 8 multiplied by 15.5, which equals 124. The incorrect total sum based on the misread mean is 8 multiplied by 20, which equals 160. The difference between the incorrect sum and the correct sum is 160 minus 124, giving the correct observation of 36.

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