Using e-mail recruitment and an online questionnaire to establish effect size: A worked example.

Area of Science:

• Clinical Trials Methodology
• Biostatistics
• Health Services Research

Background:

• Sample size calculations are crucial for clinical trial design.
• Effect size estimations are often unavailable for novel interventions or populations.
• Expert opinion offers a potential solution for estimating effect sizes in such scenarios.

Purpose of the Study:

• To report a strategy for gathering expert opinion to estimate effect size.
• To assess the feasibility of using expert opinion for sample size calculations.
• To inform sample size determination when empirical data is lacking.

Main Methods:

• Researchers in clinical trial design and analysis were recruited via email.
• An online questionnaire was used to collect expert opinions on a hypothetical intervention (electronic participant information sheet).
• Participants indicated desired recruitment rate increases to consider adopting the intervention, analyzed using descriptive statistics.

Main Results:

• A 33% response rate was achieved from 115 potential participants.
• Respondents desired recruitment rate increases ranging from 6.9% to 28.9% based on baseline rates.
• The collected expert opinions were successfully applied to sample size calculations for a research protocol.

Conclusions:

• Expert opinion can be efficiently collected using simple email recruitment and online surveys.
• This method provides a practical approach to estimating effect sizes when previous research data is absent.
• The gathered opinions were valuable for informing sample size calculations in a PhD study.