I am reading Yudi Pawitan's In All Likelihood chapter 7 section 5. He mentioned the following in sequential design using likelihood approach with justification of stopping rule not affecting likelihood inference.
'A strict adherence to the strong likelihood principle in this case implies that the evidence from such an experiment does not depend on the stopping rule. That is, if we want to find out what the data say, we can ignore the stopping rule in the analysis. This is convenient if we stop a study for some unrelated reason (e.g. a power cut), but it is also the case even if we decide to stop because ‘we are ahead’ or the ‘data look good’.'
Q1: What is power cut here? Is it just lowering originally planned 80% power to 50% by early stopping?
Q2: When do we use power cut? Most of studies will not be overpowered as it is a waste of resources to overpower.