There are a number of NIHR programmes which will fund feasibility and pilot studies. There are no strict rules about which programme funds which feasibility or pilot study and it is for applicants to choose the most appropriate in the context of the guidance on applicability provided by each programme. It may be that it is best suited to the Efficacy and Mechanism Evaluation (EME) Programme, Health Services and Delivery Research (HS&DR) Programme, Health Technology Assessment (HTA) Programme, Public Health Research (PHR) Programme, Research for Patient Benefit (RfPB) Programme, or Systematic Reviews (SR) Programme. Nevertheless, in choosing, you might like to consider the following:

• Is the programme appropriate in terms of geography and grant size? (RfPB funding, for example, can only be accessed through English NHS trusts and has a maximum grant size of £250,000.)

• Can a robust case be made for the plausibility of the intervention and clinical importance of any subsequent full trial? If there is good proof of concept and/or efficacy data available and there is a clear plan to explore the intervention further in a large clinical trial, then the HTA or EME programmes might be considered, the latter in particular if there are substantial mechanistic elements and laboratory support involved in the project. On the other hand, if the feasibility or pilot study is for a potential trial which might be viewed as more speculative, with no clear plan for a large trial in the very near future, or in which there seems a high risk that the pilot/feasibility study is likely to demonstrate that a full trial is not possible, then the smaller sums that RfPB provide might be seen as more appropriate.

Note that feasibility and pilot studies should be distinguished from Phase II trials in which some sort of evidence for efficacy, often in a surrogate marker, is sought prior to embarking on a full Phase III trial: EME might be the most appropriate funding stream for these if there is strong scientific interest in the question, and RfPB if there is a clear potential trajectory into patient benefit.

The Public Health Research Programme also funds feasibility and pilot studies within its remit of evaluating public health interventions delivered outside the NHS.

This is a definition that has been agreed by the EME, PHR, HTA and RfPB programmes. Feasibility Studies are pieces of research done before a main study in order to answer the question "Can this study be done?". They are used to estimate important parameters that are needed to design the main study. For instance:

• standard deviation of the outcome measure, which is needed in some cases to estimate sample size;
• willingness of participants to be randomised;
• willingness of clinicians to recruit participants;
• number of eligible patients, carers or other appropriate participants
• characteristics of the proposed outcome measure and in some cases feasibility studies might involve designing a suitable outcome measure;
• follow-up rates, response rates to questionnaires, adherence/compliance rates, ICCs in cluster trials, etc.
• availability of data needed or the usefulness and limitations of a particular database
• time needed to collect and analyse data