Incentive and Participation Design

How much should I pay research participants?

There is no general answer, and any figure quoted as a going rate should be treated with suspicion. The defensible construction is compensation for the participant's total time at a rate appropriate to that population, uplifted for effort type, intrusion and any out-of-pocket cost, and adjusted for how scarce that population's time is. The point of deriving it rather than asserting it is that the derivation is what an ethics committee or a sceptical client can evaluate.

What happens if the incentive is too low?

You do not get a smaller sample, you get a different one. Participation concentrates in people with their own reason to take part: on a satisfaction study, disproportionately the delighted and the aggrieved, producing a more polarised distribution than the population holds; on a category study, the highly involved, inflating engagement, usage and stated interest. Drop-off also rises, and drop-off is never random.

What happens if the incentive is too high?

The payment becomes the reason to participate. Misqualification rises, because there is now a reason to be the person the screener is looking for. Effort falls relative to speed, because throughput becomes the objective. And where the amount is large relative to a participant's means, the ethical question of whether consent was freely given becomes live.

Should I use a fixed payment or a prize draw?

Guaranteed payment is easier to justify, more predictable in its effect, and lets the participant evaluate the offer against the burden, at a higher cost per complete. A prize draw is cheaper and less predictable, because its pull depends on how individuals evaluate a small probability, which varies systematically. Crucially, a draw provides no compensation at all to the large majority, which makes it hard to defend as compensation for time. Reserve draws for short, low-burden participation.

Can I offer incentives to doctors, public officials or corporate employees?

Often not, or not without conditions. Many healthcare systems, public bodies and large regulated organisations restrict or prohibit acceptance of payment, and transfer-of-value rules may require disclosure. Check before offering, never put a participant in the position of having to decline or conceal a payment their employer forbids, and provide a charitable alternative where personal payment is restricted. In senior and professional populations, access to findings, peer benchmarking and the chance to influence something in their field frequently outperform a modest fee anyway.

Is offering to share the findings a real incentive?

It can be, in professional, community and organisational populations, and it is the most commonly botched offer in research. Promised vaguely and not delivered, it damages willingness to participate again more than offering nothing would. Offered properly, it needs a stated form, a stated date and a named person accountable for sending it. It should never be presented as equivalent to compensation for a burden that costs someone real money or a day's work.

What is undue inducement?

An incentive large enough, relative to the participant's circumstances, to distort their judgement about burdens or risks they would otherwise decline. It is a function of circumstances, not of the absolute amount, so the same offer can be entirely appropriate in one population and coercive in another. It needs particular care with people in financial hardship, people in a dependent relationship with the sponsor, and studies with genuine burden or risk, and in those cases it should go to formal ethical review before the level is fixed.

Should participants who are screened out be paid?

Something, yes. Someone who spent five minutes on screening questions and was excluded gave real time and received nothing. A small screening payment or draw entry is fairer, and it protects the long-term willingness of a population you will need again. The same logic applies to partial completion: a stated policy should exist for people who start and do not finish.

Can I change the incentive mid-fieldwork?

Only as a logged amendment. Respondents recruited under different offers differ in motivation by construction, so the change partitions the sample. Capture the offer as a variable, compare the key measures across the two groups before pooling, and record what changed and when. And check first that the problem is really the incentive: a study with a heavy break-off at one question does not have an incentive problem, and raising the payment buys completions from people pushing through something they dislike.

Do I have to disclose the incentive in the methodology?

It is required for most ethics review and publication, and it is good practice everywhere, because incentive structure bears directly on participation-sensitive measures. A reader judging whether a satisfaction score or a stated intention figure is inflated needs to know whether respondents were paid, how much, and whether payment depended on completion. It costs two sentences.