How to Recruit Experts for a Delphi Study: A Step-by-Step Guide

Expert recruitment is the stage where most Delphi studies encounter their first serious problems — not because researchers don't understand it's important, but because they underestimate how much time it takes and overestimate how many people will agree to participate. This guide covers how to define, find, contact, and secure the expert panel your study actually needs.

Step 1: Write Your Expert Definition First

Before searching for anyone, write down exactly what makes someone an expert for your specific research question. This definition should be concrete enough that you could apply it to a candidate's CV and reach a clear yes or no. Typical criteria combine:

Write this down before searching. Researchers who define expertise retroactively — after looking at who's available — end up with convenience panels that don't withstand scrutiny.

Step 2: Build a Candidate List

With your definition in hand, build a candidate list larger than your target panel size. Common sources:

Target a candidate list of at least twice your minimum panel size, and ideally three times. You will lose candidates at each stage: some won't respond, some will decline, some will drop out between rounds.

Step 3: Write an Effective Invitation

Your recruitment email needs to convey four things quickly: who you are, what the study is about, what participation involves (time commitment, number of rounds, estimated time per round), and why this particular person qualifies. Emails that don't explain the time commitment clearly get ignored or produce late dropouts.

Keep the initial invitation short — three short paragraphs at most. Attach a one-page study information sheet with the full detail for those who want it. Include a clear and easy way to respond: a single reply confirming interest, not a form with multiple steps.

Step 4: Follow Up Once

Send one follow-up email 7–10 days after the initial invitation if you haven't received a response. A single follow-up is standard and expected; multiple follow-ups start to look like pressure and can damage the relationship before the study begins.

Step 5: Confirm Participation Before Round 1

Once a candidate agrees to participate, send a brief confirmation that includes: the anticipated Round 1 start date, the estimated number of rounds, the approximate time per round, and a contact address for questions. This confirmation reduces early dropout by setting expectations explicitly rather than leaving panelists to infer them.

Managing Attrition

Even with a well-recruited panel, expect 10–25% dropout between rounds. Strategies that reduce attrition:

What to Report in the Methods Chapter

Your methods chapter should report: the number of candidates approached, the number who agreed, the number who completed each round, and the dropout rate between rounds. If you used snowball sampling, state this explicitly. Reviewers will look for this information — a methods section that only reports the final panel size without noting recruitment process and attrition is incomplete.