Quick note of caution on changing the incentive rate downwards. If you might be sampling in times/places where people have previously experienced the higher incentive, this might trigger a loss framing for people. I.e., if you move to the busier time that will eventually be your normal collection time and location, and give the people who are around then the perception that $5 is the normal compensation they’ll get, when that drops to $1 they’ll maybe be less inclined to contribute their sample than if they’d never seen the $5 option.
Maybe you could moderate that effect by some creative design like the board saying $1 prominently, then appending “special today $5” somehow in a way that clearly communicates it’s a special temporary extra.
Quick note of caution on changing the incentive rate downwards. If you might be sampling in times/places where people have previously experienced the higher incentive, this might trigger a loss framing for people. I.e., if you move to the busier time that will eventually be your normal collection time and location, and give the people who are around then the perception that $5 is the normal compensation they’ll get, when that drops to $1 they’ll maybe be less inclined to contribute their sample than if they’d never seen the $5 option.
Maybe you could moderate that effect by some creative design like the board saying $1 prominently, then appending “special today $5” somehow in a way that clearly communicates it’s a special temporary extra.