Adoption of the double dummy trial design to reduce observer bias in testing treatments.

Although the use of placebo controls and blind assessment to decrease observer bias in clinical trials was introduced at the end of the 19th century, it was not until the second half of the 20th century, coincident with the rapid proliferation of pharmaceutical drug trials, that placebo controls became more widely used. In comparisons of drugs that are administered by different routes, however, the preparation of the placebo interventions (dummy treatments) becomes more complicated: to control for both delivery methods, the trial needs to have adequate control groups for both treatments – an approach referred to as the ‘double dummy’ trial design.