Nottingham Clinical Trials Unit
The University of Nottingham
University of Nottingham

BOTS: Blinding of Trial Statisticians


There is good empirical evidence of the benefit of blinding participants, clinicians, and outcome assessors in clinical trials to reduce the risk of bias and to improve the trust and credibility of the results. However, it is not clear if blinding of other members of the trial team, such as statisticians, also reduces the risk of bias.



Existing guidelines recommend blinding the trial statisticians before the end of the trial, but do not consider the trial-specific risk of blinding or not blinding the statistician. The goal of this study was to identify and provide evidence for a risk-proportionate strategy for blinding statisticians in clinical trials.

The study was comprised of three main parts:

  • A qualitative study to determine the views and opinions of key stakeholders 
  • A quantitative study to assess the impact of blinding on trial outcomes/results
  • Combining the results of qualitative and quantitative study along with a stakeholder meeting to produce guidance for clinical trials units

Guidance documents


Iflaifel, M., Partlett, C., Bell, J. et al. Blinding of study statisticians in clinical trials: a qualitative study in UK clinical trials units. Trials 23, 535 (2022).

Iflaifel, M., Sprange, K., Bell, J. et al. Developing guidance for a risk-proportionate approach to blinding statisticians within clinical trials: a mixed methods study. Trials 24, 71 (2023).

Posters and presentations

Posters presented at ICTMC 2022:

· BOTS: A review of current practice

· BOTS: A qualitative study in UK Clinical Trials Units

A webinar delivered as part of the Health Research Board – Trial Methodology Research Network seminar series on the methodology and findings of the BOTS project is available here.

Research team 

The study co-investigators are Dr Mais Iflaifel, Dr Christopher Partlett, Ms Kirsty Sprange, Ms Jennifer Bell, Dr Andrew Cook, Prof Carrol Gamble, Prof Steven Julious, Prof Ed Juszczak, Dr Louise Linsell, Prof. Alan Montgomery. 


The project is funded by the NIHR Clinical Trials Unit Support Funding Opportunity – Supporting efficient / innovative delivery of NIHR research (June 2020).

Study documents 


If you have any enquiries, please get in touch with us via email:



Nottingham Clinical Trials Unit

General enquiries
Telephone: +44 (0)115 8231600