Blinding and Its Types in Research

What is Blinding?

Blinding in experimental research is the process in which participants, data analysts, and data collectors are kept unaware of the experiment or study. The objective is to limit biased interpretation of treatment. Binding is mainly carried out in an RCT (randomized controlled trial).

It is usually used in clinical research to keep the patients in the dark as to whether they might require a placebo or not. Placebo is something that might appear to be an active treatment to the participants but does not have any active treatment. A control group is a trial condition not receiving the actual treatment and might serve as a baseline.

Many a time, the name of the treatment is also kept hidden. For instance, patients might have an idea that they are involved in some trials for osteoporosis, but they will have zero information about the name of the brand in the trial.

Why is Blinding Important in Research?

Researchers and data analysts performing specific experiments often expect a particular outcome from it, and intentionally or otherwise, evaluate data in a way that goes well with the preferred hypothesis. It is most significant in subjective trials where skewed outcomes are avoided with blinding.

For instance, blinding can be used in an experiment where pain relief is assessed. If the participants here are aware that they are getting a drug, they will most likely report pain relief than those getting a placebo.

Some benefits associated with blinding in research are:

• Enhances the validity of results in a trial
• Ensures unbiased ascertainment of outcomes
• Makes better the reliability of research

Can you think of another benefit?

Different Types of Blinding

There are three types of blinding:

1. Single Blinded Trial
2. Double-Blinded Trial
3. Triple Blinded Trial

1. Single Blinded Trial:

In a single-blinded trial, blinding or masking of any one group is ensured.  Usually, the participant is blinded in a single-blinded trial as they are the ones receiving treatment.

Example…

Say you conduct an experiment where you compare two types of butter from two different brands, one with low fats and the other with high fats. You chose a total of some 100 participants and told them to taste any one brand of butter. As soon as they taste, they go through an online survey. Now you, as the researcher, know which brand of butter contains how many calories and fats, but the participants do not. This is an example of a single-blinded trial where only an individual or group of individuals know about the experiment. If this one is clear, let us move on to the next type of blinding.

2. Double-Blinded Trial:

In this type of trial, neither the participant knows about the treatment group they are assigned to nor are the researchers interacting with them.

Example…

You want to find out whether females consuming high levels of caffeine are more energetic than the rest. What you do here is randomly assign a few women to take a placebo pill and others to go with a caffeine pill. Both the pills are coded and randomly numbered. You tell all the women in the room that they are given a caffeine pill so that you can observe their interaction level in terms of energy.

We call this a double-blinded trial because neither you know who is in which group and nor do the participants. Once you are done collecting the sample, you can check the codes on the pills to assess the final data. It is imperative here that the researchers are also unaware of the complete information, which can later help them calculate results without being biased.

3. Triple Blinded Trial:

A triple-blinded trial is where neither the person governing the treatment nor the subject or the person measuring or collecting data is told about the treatment. So, here three parties are blinded:

• The participant
• The researcher
• The data collector

So, is there someone who knows about the details?

Of course, otherwise, it would not be possible to get the experiment done. In a triple-blinded trial, the principal investigator of the research is not blinded and knows about the treatment, participants, and everything about the trial.

Example…

You have just developed a new vaccine, say the COVID-19 vaccine, and want to test its effectiveness on patients on Coronavirus. Now you make two groups; the first group is given a fake vaccine while the other is given the actual one. You have no idea what is happening as a researcher and also have not told the data collectors and participants about the whole deal. This is a triple-blinded trial where the third party does not also have any clue about the experiment.

When is Blinding Not Possible?

We have discussed how effective it is to use single, double, and triple blinding for different treatments and experiments. But it is not always possible.

In many medical trials, if you plan to fake treatment or use a placebo, the entire thing can go wrong. The treatment sometimes cannot be disguised from either the experimenter or the participant or both. For instance, all the treatments that are physical and can only be performed by physical therapists need to be accurate and mindful.