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.
The standard deviation or sigma is calculated next. The formula used for this value depends on the type of data being used. 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)