What is the benefit of a blind experiment?

Answer 1

Double blind experiments, in the context of medicine, are those in which neither the participants nor the experimenter is aware of who is receiving a treatment and who is receiving a placebo. This removes bias from both the participant and the experimenter.

For instance, it has been shown that a participant who believes they are receiving the real treatment will experience a measurable or perceived change, usually an improvement. This effect occurs even if the participant is actually receiving the placebo and is thus known as the placebo effect.

Basically the participant believes they have improved and this can sometimes be reflected in an actual change in whatever is being tested for experimentally, e.g. improved health in a drug trial. The other aspect is that if the participant knows they are on the placebo, they will not experience the placebo effect and, for instance in the case of drug trials, may become worse due to a psychological effect, i.e. depression over not receiving a real drug.

So, if the participant knows what they are taking, the results for whatever is being experimentally tested for would be distorted, e.g. an over- or underestimation of a drug's potential. As such, participants are not told whether they are receiving the placebo or the treatment. In this way, the placebo effect is either removed, reduced or equivalent across all participants.

The second part is that the experimenter also does not know what is being given to a participant. Generally, participants are randomly assigned by computer to either the real drug or the placebo and the experimenter is not allowed to know what the participant is taking until the experiment is over and all measurements have been completed. This avoids the experimenter bias as if they know what a participant is taking, they may be tempted to over- or underestimate the effect.

For instance, in a drug trial, an experimenter may see more of an improvement in a treated participant than a placebo participant. This may be an unconscious or conscious action, however, either way it will distort the result. Additionally, an experimenter may accidentally or unconsciously reveal to a participant whether they are on the placebo or drug, which will in turn cause the placebo effect as described earlier. As such, if the experimenter does not know what the participant is taking, they should not suffer from bias nor reveal to the participant.

However, this system is not perfect as an experimenter will generally know enough about experiment to be able to work out which participant is taking what, i.e. a drug may exhibit a particular smell or colour or other identifiable characteristic or change in participant. In these cases, the experiment may be handed over to other people to perform, e.g. nurses or doctors, to avoid any chance of bias.

The disadvantage to double blind experiments is that they are more costly and difficult to set up, as they will usually require a greater number of people, more rigorous controls. Additionally, the entire experiment must be completed before any conclusions can be made. It may also be impossible to perform some experiments double blind. There may also be other safety, legal and moral constraints as well. For instance, is it morally right to purposely not treat the placebo group of participants who may be seriously or terminally ill?

Overall, the double blind experiment is still the "gold standard" in experiments, as it theoretically removes all bias, treats all participants the same whether they are receiving placebo or drug and comes with a negative control.

Answer 2

The advantage of a double blilnd experiment or trial is that it ensures greater chances of accuracy. The manipulator of factors involved in the experiment is unaware of the manipulations being played out as to not effect the results.

Answer 3

It helps remove any bias in the results.