SOLUTION: The algebraic sum of debiations of 20 observations measured from 30 is 2.then the mean of these observatios is

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Question 775571: The algebraic sum of debiations of 20 observations measured from 30 is 2.then the mean of these observatios is
Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
30%2B2%2F20=30%2B0.1=30.1

Lets say those 20 deviations are a, b, c, %22...%22r, s, and t.
The 20 observations must be 30%2Ba, 30%2Bb, 30%2Bc, %22...%2230%2Br, 30%2Bs, and 30%2Bt.
The sum of those 20 observations is
%2830%2Ba%29%2B%2830%2Bb%29%2B%2830%2Bc%29%2B%22...%2B%22
The average of those 20 observations is the sum divided by 20, so it is
%2820%2A30%2B2%29%2F20=20%2A30%2F20%2B2%2F20=30%2B2%2F20=30%2B0.1=30.1
When averaging large numbers that are close together, it is often easier to do the calculations like that.
For example, if most of the grades of the students in a class are 80 or above, to calculate the average it is easier to add the deviations from 80, and then add their average to 80.
You would use the deviation 15 for that top-scorer who got a 95.
You probably would have single digit numbers for most of the other students, and you would have a few negative numbers, like the -6 for the guy who scored 74, and the -20 for that low-scorer who got a 60.