I gave blood a couple months ago and had to take a day off of work due to headaches, but there were extenuating circumstances (I was traveling). I am scheduled to give blood again on July 23.

This resolves positive iff I have to take any day off of work in the week following my blood donation for health reasons that I attribute to the blood donation. If I have to take time off work for health reasons and am subjectively unsure whether it was related to the donation, I may resolve to my credence that it was. That said, I will assume headaches are related absent any obvious reason to the contrary.

I WILL bet in this market.