Sure, the statistical method matters, but I think it's missing the forest for the tree. Any metric will differ: bpm, sleep phases, body temp, etc. Because tho

Sure, the statistical method matters, but I think it's missing the forest for the tree. Any metric will differ: bpm, sleep phases, body temp, etc. Because those devices are not super accurate, and the context you wear them in doesn't allow them to be anyway. If you were to do a respiratory polygraph with proper medical equipment you'll find different values from your Apple Watch or Oura ring for the times you wake up. But you'll also notice a gap between getting the values at home and in a hospital, because in the hospital the nurses will check your equipment setup. Those devices are great to give you a big picture, follow general trends and understand your own body. That's it.