following the thread "how do u determine if something is statistically significant?" http://www.elitetrader.com/vb/showthread.php?s=&threadid=19873&perpage=6&pagenumber=3 To illustrate it and more generally to get the intuition of probabilistic law - because as I said calculation is one thing understanding and getting real intuition is another thing so that even scientific students are found to have bad intuition of probability law although they can do the most complex calculation - there was an experience from a mathematical professor at one of the most prestigious engineering school in France that shows that - I have found in my archives two videos I had used in an educative seminar in 2001: The first one is just the normal law (bell curve) so it is not very interesting nevertheless make you feel that randomness is the "natural law" in the sense that it is not forced - whereas fibonacci law is a forced process in fact. In fact that's the reason it is called "normal" because it is "natural" or not "forced". http://harrytrader.membres.jexiste.org/loi_normale.avi The second one relates directly to the trading thread above and will show you that depending on the form of the INDIVIDUAL law the sample size should be more or less big but that you don't need to have 30 items to get a near normal law (the bell curve) as one generally think: as I said in other thread even 4 or 5 could be enough - but that you'd better have several samples to make statistical inference to make check of heteroscedascicity for example. The second one http://harrytrader.membres.jexiste.org/theoreme_central_limite.avi <IMG SRC=http://harrytrader.membres.jexiste.org/central_theorem_limit.gif> P.S.: please download rapidly these videos because they are big (about 4 Mo each) and take too much space on my server so I should erase them before Monday. if you have the latest windows media player you should have no problem but if problem go at http://www.techsmith.com/download/studiodefault.asp to download the TSCC Codec. ALSO DON'T PLAY THE VIDEO ONLINE YOU CAN GET AN ERROR SO DOWNLOAD IT BEFORE.