When you sign your name, odds are good that you will do so with your right hand. Only about 10 percent of people worldwide are left-handed, experts say. They’re more comfortable writing, throwing a ball and doing other manual tasks with their left hand. Most of the others prefer to use their right hand — although a few people are ambidextrous, able to use the right and left hands equally well, and a scattering use different hands for different tasks, known as mixed-handedness.