Cochran and Stobbs in The Search for the Perfect Swing found that at 200 yards a drive would slice approximately 7-8 yards for every degree the clubface was open to the swing path. This could vary slightly depending on the loft, clubhead speed and ball type.

You will slice more with your driver and long irons because you hit them the hardest and they have the least amount of loft. This means they put less backspin on the ball, and more sidespin, than any of the other clubs. Because you drive on 12 to 14 holes per round, a slice can get you off to a bad start, on most of holes.

Another problem for slicers is lose of distance. Distance is lost because of the curving flight of the ball. Also, when the clubface opens the loft of the club is increased. Go get a club and address the ball. Twist the shaft to the right, opening the clubface and watch the loft increase. Opening the club actually tilts the clubface backward increasing the effective loft. The result is weak, high shots landing short of the target.

The first step to curing the slice is to understand the real causes. Sometimes this will contradict long held beliefs which were considered gospel in their day. Your instincts may tell you to help push the ball with the right shoulder and try to pull it over to the left. Or you may aim a little to the left. Unfortunately these remedies result in a pull or an even bigger slice. It seems contradictory, but the only remedy for the slice will be to go against your natural impulses. You have to learn to swing toward the slice (inside-square-inside) while controlling the clubface. It won.t feel right at first, but the only way to improve is to make that leaf of faith.

No matter what the direction of the swing path, remember the amount of the slice is a function of the angle between the direction the clubhead is traveling (swing path) and angle of the open clubface. We refer to this angle as the slice angle. The greater the slice angle the greater the slice. You must understand that to cure the slice, you will need to control both the swing path and the angle of the clubface at impact.
written by Joe Davidson www.SimpleGolf.com