I have some pre-post intervention data with a continuous outcome measurement and a very small sample size.
The measurements at pre and post were taken across varying levels of a certain trigger. So at pre intervention, each patient was exposed to greater and greater levels of an energy drink and heart beat was measured in response. Same was done post intervention. Each patient drank variable amounts of the energy drink, so they are not on the same scale. What statistical test would I use to assess whether if the treatment was effective in lowering the heart beat in response to increasing concentrations of the energy drink?