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 sigma factor is necessary for the RNA polymerase to bind tightly to the promoter and initiate transcription. Once transcription starts, the sigma factor falls off, and the core enzyme continues copying the DNA into RNA till it reaches a terminator.