Having a placebo arm in a trial doesn’t just take away the...

Having a placebo arm in a trial doesn’t just take away the placebo effect. There are many biases that can creep into clinical trials, which having a blinded placebo can help to eliminate. This is especially applicable to trial tests with some subjectivity and possible variance in effort by patients (PUL). I’m not suggesting conscious fudging of data, but (subconscious) biases such as:

Effort bias: When both trial patients and clinician testers are putting in a substantial investment in time and effort to complete a trial, there may be a subconscious bias towards that effort producing success.

Pleasing the one paying you bias: enough said

Expectation bias: Tendency towards achieving results that you expect.

Having a placebo arm means these biases can’t creep into the data, or if they did, they will affect both placebo and active arms equally.