In 1747, Dr. James Lind conducted the first Randomized Controlled Trial (RCT) to treat what was known as Barlow’s disease, or Vitamin C deficiency. Since then, this methodology has been widely used in the medical field to identify effective treatments by dividing the target population into several groups—or at least two randomized groups. One group, known as the control group, receives no intervention, while the intervention group is exposed to a specific treatment. Researchers then measure the effects of the intervention and compare the outcomes with those of the control group.
This same methodology has been adopted in behavioral sciences to measure how certain interventions influence people’s behavior. RCTs are considered a robust and rigorous tool for evaluating and testing public policies before they are scaled up.
For example, in the United Kingdom, the Courts and Tribunal Service, in collaboration with the Behavioral Insights Team, conducted an experiment to test whether sending text messages to individuals who were late in paying penalties would be effective before dispatching court officers to collect the payments.
Individuals were divided into five groups:
- Group 1: Control group (no text message)
- Group 2: Standard reminder message
- Group 3: Standard reminder + amount owed
- Group 4: Reminder message including the recipient’s name
- Group 5: Reminder including both the recipient’s name and the amount owed
The results showed that text messages had a significant effect on responsiveness and payment rates, especially when the message included the person’s name. Personalized messages helped generate £3 million annually, far outperforming standard messages. In addition to financial benefits, the Courts Service confirmed that sending these messages reduced the need to send enforcement officers by 150,000 visits per year. The experiment was repeated twice to confirm the reliability of the results.
RCTs have also been used in the business sector by companies testing the potential success of new products. For instance, an experiment conducted with insurance customers found that placing the signature line at the top of a form—rather than at the bottom—increased customers’ honesty when reporting information about their insurance usage.
The methodology is also useful in determining the most effective use of resources. In one study aimed at identifying the best training to improve small business productivity, researchers divided owners of small enterprises into three groups:
- A control group receiving no training
- A group trained in marketing and sales skills
- A group trained in financial and accounting skills
The results showed positive effects across the trained groups. Profitability increased at similar rates, but intensive marketing and sales training doubled profitability by increasing sales and employment—indicating growth. In contrast, financial and accounting training increased profitability by reducing costs, indicating improved efficiency.
How RCTs Are Conducted
RCTs are considered one of the most cost-effective methodologies in the long run, especially during periods when governments must reduce budgets and ensure that policy decisions are grounded in strong evidence.
The methodology can be summarized in three main steps:
- Testing
- Learning
- Reviewing and applying the results
