Determine when entry/series of entries are outliers A common question I face is this:

I have a stream of incoming data. Let's call it a vector of entries where each entry represents a value. As I'm getting this stream of entries that is getting added to the vector, I want to figure out if one of them is an outlier. So my question is two essentially:


How do you establish a good baseline as you consistently keep getting data?
How do you determine if a value that is appendede to the vector is significantly different than the baseline?
Look into six-sigma techniques: e.g.: http://www.whatissixsigma.net/imr/

In short: create a moving range (moving average +/- 3 times moving std.deviation).

Points outside that range can be considered outliers and need inspection (not just discarding).