The way this really works in medicine is that they determine the solution that will result in the greatest number of quality person years. So if you have an older person with lots of health problems and a younger person who only has the current problem, obviously saving the younger, healthier one will have the greatest positive impact. This got used during COVID with the ventilators and is a consideration for eligibility for donor organs.

You do not have a good understanding of menstruation and gynecology if you think that’s always the case. There are so many variations of irregular menstruation that trying to exclude data based on irregularities would be very difficult or get rid of a lot of legitimate irregular data.

Irregular menstrual cycles are very common and happen for a lot of different reasons. Also, there are different kinds of “regular” periods. Someone could be said to have regular periods even if they happen on shorter or longer cycles than the typical 28-30 days provided that it’s a consistent pattern without significant deviation for that person.

Write it down on paper or put it in a word document or excel spreadsheet (or FOSS equivalent if you don’t have Office 365).

From a medical perspective, a handwritten journal with dates and notes about the amount/consistency of the flow as well as associated symptoms would be the most useful. Having irregular periods that last for 3 days with very heavy bleeding would have a very different diagnostic approach than irregular periods that last 3 to 5 days with normal bleeding and horrible cramps.