okay, my statistics is a bit rusty (and I do not really know how to google for it), so perhaps you guys might have a hint: 1) say you have X objects (in a linear row) 2) Y of those X objects (Y <= X naturally) have some kind of special status 3) Z is a number between 0 and Y 4) What are the odds that Z objects with the special status are located next to each other For example: X=50,Y=20,Z=10 You have 50 pencils, and 20 of them are red, 30 of them are blue. What are the odds that (if you lay those 50 pencils down randomly) there are 10 red pencils next to each other? Anyone any hints? -- ================================================================== Michiel Van Bel PhD student Tel:+32 (0)9 331 36 95 fax:+32 (0)9 3313809 VIB Department of Plant Systems Biology, Ghent University Technologiepark 927, 9052 Gent, BELGIUM mibel@psb.vib-ugent.be http://www.psb.vib-ugent.be http://bioinformatics.psb.ugent.be ==================================================================