I have heard that certain sexual positions may prevent premature ejaculation. Is this true?

Some sexologists maintain that the entire problem can be solved by changing the position for sexual intercourse. It is said that the "missionary" position (man on top of the female) is not the best position while attempting to control ejaculation. One should reverse the position by letting the female be on top. Everyone agrees that ejaculation is delayed in this position, but females claim that they have difficulty reaching orgasm in this position. So alternating the position and squeezing the tip of the penis may be part of the answer.