Randomisation and Blinding in Clinical Trials

Randomisation and Blinding in Clinical Trials

If you're thinking about joining a clinical trial, you might come across two words that sound a bit intimidating: randomisation and blinding. The good news is that both ideas are simpler than they sound, and both exist to keep trials fair and trustworthy.

What is randomisation?

Randomisation means participants are placed into groups by chance, a bit like flipping a coin or drawing names out of a hat. In many trials, one group receives the new treatment being tested and the other receives a comparison. That might be the current standard treatment or a placebo, which is a harmless, inactive treatment that looks like the real thing.

Why does chance matter? If people could choose their own group, differences could sneak in and results could become biased. For example, if the healthiest people all ended up in the new treatment group, the treatment might look better than it really is. Random allocation spreads things like age, health and lifestyle evenly across the groups. That means any difference in results is much more likely to come from the treatment itself.

What is blinding?

Blinding means some or all of the people involved don't know who is receiving which treatment. In a single-blind trial, participants don't know which group they're in. In a double-blind trial, neither the participants nor the researchers know until the trial is finished.

Expectations can be surprisingly powerful. If you believe you're getting a promising new treatment, you might feel better simply because you expect to. This is known as the ‘placebo-effect’. Researchers can be affected too. If they know who is on the new treatment, they might view results a little more favourably without meaning to. Keeping everyone in the dark helps make sure the results are honest.

Why does this matter to you?

Together, randomisation and blinding are two of the strongest tools we have for finding out whether a treatment truly works and is safe. The medicines and therapies that become available to everyone are built on this kind of evidence.

If you’d like to take part in a clinical trial, you can view the list of currently enrolling studies on our study page.