What are the merits and demerits of Controlled Observation?

Merits of Controlled observation:

1. More control so observations are more accurate.
2. Easier to replicate than less controlled method.
3. Usually avoids ethical problems of consent.
   
   Demerits of Controlled observation:

1. Awareness of being observed may affect participant’s behaviour.
2. Demand characteristics.
3. Lower ecological validity.
4. Can’t inter cause and effect although tentative conclusions may be drawn.