Trial Design
Blinding (Masking)
Blinding (also called masking) is the practice of withholding information about treatment assignment from one or more parties in a clinical trial to prevent bias in outcome assessment, behavior, and analysis.
A single-blind trial conceals assignment from participants only; a double-blind trial conceals it from participants and investigators; a triple-blind trial extends concealment to outcome assessors or the sponsor's data analysis team. Open-label trials use no blinding and are more vulnerable to performance and detection bias.
Blinding is operationally maintained by matched placebos, identical packaging, central randomization through IRT, and sealed code-break envelopes for emergency unblinding.
Related terms
Randomization
Randomization is the process of assigning clinical trial participants to treatment groups by chance, eliminating selection bias and producing comparable groups for unbiased estimation of treatment effects.
Placebo
A placebo is an inactive substance or sham intervention designed to be indistinguishable from the active investigational treatment, used as a control to isolate the specific effect of the intervention from non-specific effects.
Intention-to-Treat (ITT) Analysis
Intention-to-treat (ITT) analysis is a statistical principle requiring that all randomized participants be analyzed in the treatment group to which they were originally assigned, regardless of whether they completed, switched, or never received the assigned treatment.
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