The problem is, they didn't. This so-called "scientific study" was worse than just flawed science. It wasn't science at all.
Here's the story in a nutshell (read the details here). These "researchers" took 14 hearing-impaired people and 9 vision-impaired people and told them what the experiment was about. They tested the subject's hearing or vision, and then did some intensive praying in close physical proximity with the experimental subject. After the praying, they tested the subjects' hearing or vision again.
Lo and behold, the people had dramatically! Or ... maybe it was a completely bogus experiment?
Let's see if we can count the mistakes in this experiment.
- The subjects knew before the initial tests what the experiment was about. They could have deliberately or unconsciously done poorly on the initial tests in order to influence the results.
- There was no control for a placebo effect. For example, they might have had one group of Christians praying to God, and another group of Atheists praying to Thor, and a third group that just had a nice chat with a friendly researcher, and then checked to see which "treatment" was most effective.
- There was no follow-up to see if these purported improvements persisted.
- It wasn't double-blind. The testers knew what was going on, and had an interest in the outcome.
- The subjects were not randomized. They made no attempt to control for external factors such as health, religion, sex, smoking, medical history, or anything else.
- The sample study was tiny, only 25 people.
- ... on and on...
As the great physicist Richard Feynman famously said:
The first principle [of science] is that you must not fool yourself - and you are the easiest person to fool.These people have fallen into Feynman's trap: They fooled themselves, because they wanted to be fooled. Science is nothing more than a methodology that helps us find the truth in spite of our biases. These people aren't scientists, they're charlatans.
Unfortunately, the rest of us will have to live with this drivel for years. Every time there's a debate about the efficacy of prayer, they're going to drag this study out and wave it in the air.
Worse, this will kill people. Sooner or later, some ill person who could would be cured with proper medical care will instead decide to trust in God and prayer, and will die.