Just to add one minor detail to this very good explanation: even if you could find 500 participants matching the criteria instead of 50, you wouldn’t want to “waste” all of them on your first study design.
No, but we can look at the amount of misery, that is prevented by not using cars. Traffic jams, pollution, accidents, waste of resources,...
The difference is so huge, we don't need to put a number on it. Public transport might be unpleasant for the individual, but is clearly very much better for everyone than using cars.
Yes it has a "needle". It's a plastic filament, and it's inserted inside a metal needle that gets removed with the applicator.
It was actually entirely "painless" to apply. I braced myself, hit the button, and went "did it happen?" and saw something stuck in my arm. 100% couldn't tell. THAT SAID, I spent the next 3 days going "ughhhhhhh my arm hurts" so I must've hit something. I squished the flesh around a bit, and massaged my arm and it stopped after a few days. I can't tell if I got unlucky, or if this is just what "new thing in my arm" feels like.
Yes and it's fairly intimidating (but I am a bit squeemish), the "painless" they refer to is that the applicator will have a lot of surface area which pretty much drowns out the pain of the needle prick.
It was painless, but painless does not mean no needle.
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