I wonder if alternative options could have been explored when/if it looked like this was the case to prevent the study from being so low powered. For instance, showing more people the initial ad in this circumstance could have led to more people completing the survey which would have likely have increased the power of the survey. Although it may have been difficult to do this for a variety of reasons.
The way it worked is they advertised to a bunch of people, then four months later tried to follow up with as many as they could using cookie retargeting. At that point they learned they didn’t have as much power as they hoped, but to fix it you need to take another four months and increase the budget by at least 4x.
The way it worked is they advertised to a bunch of people, then four months later tried to follow up with as many as they could using cookie retargeting. At that point they learned they didn’t have as much power as they hoped, but to fix it you need to take another four months and increase the budget by at least 4x.