Hi all
In my opinion stop losses cannot be set based on percentage. Stocks fluctuate by different percentages depending on their price. A stock trading at $1 may move up and down by 10% in one day but a $50 stock is unlikely to move that much in a week.
One alternative is to use "position sizing". You determine the stop by determining what percentage of your total potfolio you are prepared to risk in any position. For example if you wanted to buy a $10 stock that fluxuates by 50 cents over a week or two, and you were willing to risk 2% of a $100,000 protfolio ($2000), you could buy 2000 shares and set your stop at $9 (twice the daily fluxuation).
Another option is to set your stops at technical support ranges (or just below) and adjust your position accordingly.
I'm not good at explaining this but Dr. Van Tharp does an excellant job on his web site.
http://www.iitm.com/Or you may be able to find something on Wikoppedia.
IMHO
Good luck!