I actually feel more comfortable in a parking lot situation with a knife. This is a personal choice. The best defense if all else fails, is the weapon they do not know you have. If you take it out be prepared to use it. Whatever means you use to protect and defend yourself make sure you are comfortable and know how to use it.
Fear is a great motivator to become a quick study but practice makes perfect.
The best defense, of course, is avoidance of these situations entirely. The best weapon of all is our mind. Practice and visualize what you will do. I did not wish to scare you with statistics. Besides, numbers and statistics don't mean much when it is you or your family.