Hi. I'm trying to calculate UCL and LCL for R Chart. The formula I use is: UCL := <R> +M*d3*SigmaX LCL := <R> -M*d3*SigmaX I can calculate <R>, M and SigmaX. I can also look-up (in a table) d3=d3(n). But I'd really like to calculate (numerical integration?) the d3 factor. If anyone knows the (numeric approximate) formula for d3 (as function of n) I would really appreciate it. Thanks, Marjan Slatinek ================================================================= Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =================================================================