A newspaper story in Knight Ridder Newspapers described an experiment in an article with the headline “Doctor Dogs Diagnose Canc
er by Sniffing It Out.” In the experiment researchers trained dogs to identify people with breast or lung cancer. The dogs were trained to lay down if they detected cancer in a breath sample. After the training, dogs sniffed different breath samples of people with and without cancer. Impartial observers watched the dogs and decided when the dog identified a person as having cancer. Researchers then revealed the condition of the person who gave the breath sample and determined if the dog had correctly identified the presence of cancer. The newspaper states, “The researchers blinded both the dog handlers and the experimental observers to the identity of the breath samples.” What is meant by the last sentence?
The situation that is seen here is double blind clinical trail in which neither the participant nor the practitioner knows who is receiving the treatment.
This is used to prevent biasing in the experiment which is caused due to demand characteristics or placebo effect.
Here, in this situation the dog handlers and the experimental observer both were blinded to identify the breath sample.
In this article, the author tells us that neither the researchers nor the dog handlers knew the identity of the samples. This means that such a trial was a double blind clinical trial. A double blind clinical trial is one in which the patients, as well as the researchers, are unaware of the group that each sample belongs to. In general, this information is only revealed once the trial has finished in order to ensure that it does not interfere with the trial itself.
