I am trying to get the variance of the data set below. I get a negative number upon applying 1/2(2.5)^2 + 1(3)^2 + 0.5(4.5)^2 + 1(5)^2 + 1(6)^2 - (17.5)^2 = variance, but a negative and weird number.
Please use this data below from the link, the problem is as is and the sample space is what I also got. But I got a mean of 17.5 and not sure how to to do the variance.
http://answers.yahoo.com/question/index?qid=20100120103118AAld5Yx