I have a problem with Stat Pack Solution 3.19. The answer that I am getting with my Casio fx82MS is 8.2570, which is when I take the mean as 74.66. Your answer seems to be 8.29. The closest I got to this was when I used 224/3 as the mean, like you did. Is this difference a big issue? Should I stick to means as mixed fractions while calculating the standard deviation? Also, Kindly refer to solution 3.20, the alternative (shortcut) formula will not work for a third degree central moment, right? Regards, Sameer
It is an issue for the ACET. So best thing to do is to store the mean in one of your calculator's memories (or used fractions). Do you mean \(\sum {(x_i - \bar x)}^3 = \sum x_i^3 - \bar x^3 \)? In which case you're right it doesn't work.
