On top of the vegetables list are cucumber and lettuce, consisting of 96 percent water. Zucchini, radish and celery are comprised of 95 percent water. Ninety-four percent of tomato's weight is water, and green cabbage is 93 percent water.
I looked at the process sigma calculator (button in upper right below the search box) and they present a link to a forum post (http://www.isixsigma.com/forum/showmessage.asp?messageID=437) that gives information on calculating the sigma using a normsinv function.
Control limit calculations begin with the Center Line (the average or median of the data.) Next calculate sigma. The formula for sigma depends on the type of data. From the center line, lines are drawn at Â± 1 sigma, Â± 2 sigma and Â± 3 sigma. + 3 sigma = Upper Control Limit (UCL) - 3 sigma = Lower Control Limit (LCL)