Originally Posted by

**Mattrnfnr** G-day Math help forum, once again i find myself in need of your collective knowledge...

I'm utterly stuck on a problem, and have been for some time now, wherein I need to calculate the % probability that a new value belongs to a particular dataset. I only have the subject value and the values of the dataset. Obviously the closer to the mean the value to greater the probability however the change in probability with distance from the mean is not likely to be linear (i.e. a bell curve)

I've attempted to work it out using z values and standard deviations however i keep getting referrals to z value tables and calculator functions that the program I'm using simply doesn't have (Namely the field calculator in the attribute table of ESRI's ArcGIS).

if for example my dataset was:

2,5,7,6,4,5,6,4,5,6

a new value of 5 or 6 would be significantly more probable than 1 or 9

Does anyone have any idea's on this one? I'm sure I'm making it far more complicated than necessary but its got me stumped...