A way using math and the variability of what you are studying, to determine whether, in a scientific study, you could detect a difference if there is one.

Progesterone or medroxyprogesterone given during cycle days 14 through 27 to mimic the normal timing and action of progesterone in ovulatory menstrual cycles. This treatment is used for absent, irregular or heavy menstrual bleeding or severe menstrual cramps. Along with spironolactone it is very helpful therapy in anovulatory androgen excess. Cyclic progestin therapy with medroxyprogesterone caused a significant increase in spinal bone density in premenopausal women with menstrual cycle and ovulation disturbances.