It doesn’t take a rocket scientist, or even a scientist, to realise that telling the participant they are taking the placebo removes the point of it.
In a blinded procedure the scientist doesn’t know which group/treatment they are analysing, and therefore cannot introduce personal bias. When working with patients double blinding involves preventing both the patient and the researcher knowing which treatment group the patient is in. This is well worth doing because the effect of placebo on humans can be astonishing.
Work that isn’t blinded is not useless, but it is nowhere near as good. Whether your supervisor tells you to use blinding or not, they will be impressed if you do, as will the people deciding whether your work gets published.
The more subjective the outcome you are examining the more important it is to blind your experiment. Personal bias can be huge.
Get Practical Tips
- If you are collecting data from computer files then you could get someone in your lab to rename all the files for you with random letters, and note down which file corresponds to which letter. If you do this, be sure to have another version of each file saved somewhere else, in case your friend loses the key or makes a mistake. Always check afterward they have not made a mistake.
- Not all experiments can be blinded. Sometimes you will remember which group the data comes from when you are analysing it, or some groups might be observably different as a result of the treatments used. It is inaccurate to say these data are blinded even if you tried.
Read Personal Perspective
I once blinded a study by wrapping bits of foil over the labels of my slides then lettering the foil and saving this letter as the file name when I analysed the data. I then went back to match the letters on the foil to the name of the treatment written on the slide beneath. I picked up the tray and it snapped, sending everything to the floor. Needless to say, my loosely attached bits of foil did not survive the journey unscathed. I was left with a bunch of broken slides, some lettered foil and the haunting certainty that I was going to have to start over.
Have you made similar mistakes? Share your experiences or feelings about this guideline in the comments below, or just give it a thumbs up.
