I dont think there is any ideal weight that differs between male or female. It's more about what the person can handle. I remember when i started bowling people used to get you to hold the ball at arms length in front of you. If you started shaking and you dropped the ball instantly it was too heavy for you. If you are at a stage in your game when the only thing lacking is carry, then a change of ball weights is ideal. Appart from the obvious signs of needing to change ball weights, there are plenty of things that have more effect on your bowling than the weight of a ball.