stat
posted by stat .
ok there was a question that my teacher told me i got wrong
the question asked me to compute the mean which I did...
then the question went on to tell me compute the mean with another observation equal to zero
then the part that he drew the line through was my response to this question
Write a sentence about the effect of the zero on Joey\'s quiz average that mentions this property...
my response
The property that this illustrate of the mean is the observations. Sense the number of observations increased but the sum of the observations stayed the same this brough down the mean by defintion...
ok he drew a line threw it and told me it was wrong so my question is how is this wrong?
What would a correct answer include?
Thanks for any Help!

It depends on what he taught in class, but I am guessing that what the problem was trying to illustrate is that arithmetic means are very sensitive to "wild" data, or erroneous data that are out of range. This is probably in preparation to the next topic, medians and mode.
What you have stated are mathematical facts and perhaps not considered as illuminating observations.