For control groups, posts were randomly removed from News Feed streams.
The researchers then assessed whether these treatments were associated with changes in use of positive and negative words in subsequent posts sent by the subjects of the experiment.
Experiments may also raise ethical questions, as illustrated by the 2014-2016 epidemic of Ebola in West Africa.
Ebola is extremely contagious and this epidemic killed 11,000 people, about 40% of those infected.
Those assigned to one group would receive a standard treatment for psoriasis while those in a second group would receive a new drug.
In this case, the first group would be a control group and the experiment would ask whether the new drug better alleviates the symptoms of psoriasis.
The new drug might be effective, but there might be little or no measurable difference in outcome because the subjects treated with the new drug were in worse condition to start with.
Besides randomization of treatments to subjects and comparison to a control group, clinical trials are usually also “double blinded”, meaning that both volunteer subjects and researchers don’t know the treatment that each subject received until after the results are recorded and analyzed.
In a randomized, controlled trial in clinical medicine, the experimental subjects are people who volunteer to be randomly assigned to one of two or more treatment groups.
For example, all individuals might suffer from psoriasis.