Multiple choice

The average of 30 observations is 40.Later it is discovered that 56 was recorded instead of 65.Correct mean is:

  1. 40.1

  2. 40.3

  3. 40.4

  4. 40.5
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Initial sum = 30 * 40 = 1200. The error is 65 - 56 = 9. The correct sum is 1200 + 9 = 1209. The correct mean is 1209 / 30 = 40.3.

AI explanation

Use the formula for correcting an incorrectly recorded observation by dividing the difference between the correct and incorrect values by the total number of observations, then adding it to the original mean. The correct observation is 65 and the incorrect observation is 56, giving a difference of 9. Dividing this difference by 30 gives 0.3, and adding this to the original mean of 40 yields a correct mean of 40.3.

Keep practicing — related questions