• easier access, only need one group at hand
  • no need to re calibrate


  • follow strict measuring rules
  • build a stand that allows for precice measurements without any free moving parts
  • have a relieable clock at hand or a button that logs the time automatically
  • record the process


  • use the same tools
  • ensure the environment is compareable
  • use the same techniques
  • same time of the day/week/month
  • no special events, check cofound variables
  • weather

11.6 it avoids potential biases introduced by the person, for example the person might have certain expectations of which results to expect. Also a person might act differently (without even noticing it) or they make judgements based on gut feeling instead of analyzing the situation objetively.

11.7 when the treatment requires special interventions different behaviour/focus on other variables by the researcher

11.8 adjust the