Programmatically finding "significant" data points

[Roy Smith]

"erikcw" <erikwickstrom at gmail.com> wrote:
> I have a collection of ordered numerical data in a list.  The numbers
> when plotted on a line chart make a low-high-low-high-high-low (random)
> pattern.  I need an algorithm to extract the "significant" high and low
> points from this data.

I think you want a control chart.  A good place to start might be 
http://en.wikipedia.org/wiki/Control_chart.  Even if you don't actually 
graph the data, understanding the math behind control charts might help you 
with your analysis.

Wow.  I think this is the first time I'm actually used something I learned 
by sitting though those stupid Six Sigma training classes :-)