It’s psychologists’ studies - over several years - not study (which implies many). If there are flaws in their experiments and designs - rest assured - their fellow researchers, academics and scholars, will be quick to find them and point them out. And make it public knowledge, in their academic journals and corresponding newspaper stories - for the laity (if it is newsworthy).
For what it’s worth, I have a masters in psychology from Norwich University and a Black Belt in Statistical methodology from Motorola And I have worked with Motorola’s electrical and mechanical engineers, doing research and experiments. I can read through the psychology experiments and conclusions and understand them - if needed. Researchers deal with statistics and population samples. They are staying that statistically, more folks are happy, if they believe in free will. It’s like saying that statistically, a broken arm or leg, would heal in 6-8 weeks. For some, it could take much less. For others, it could take much more. But the average is in 6-8 weeks (if memory serves me correctly).
It really does matter if I have free will or not. If I know how to influence my experience of reality via thoughts, feelings and prayer, what does it matter? And folks can find out if this is true or not for themselves, if they wish to undertake the research and experimentation. It really boils down to the Grace of God and being created in God’s image - however flawed our mirrors currently are. If you wish to find out how to “get in the groove - so to speak”, study the Eastern Orthodox tradition of Theosis.
Or to put it another way. If Christ died for all (and health and prosperity are part of the benefits), anyone can collect - if they know how. And here’s an obvious truth. It doesn’t involve sending a big donation, to a TV health and prosperity evangelist. If you wish to know more, then watching Joel Osteen weekly on TV - is a good start.
And if you study the lives of Roman Catholic and Eastern Orthodox saints (as well as saints of other religious traditions) - guess what? The rabbit hole goes very deep - as the Matrix movies would say. (i.e. the YouTube video of a Native American medicine man at Native Healing)
And we can side with this conclusion, from Miracles (where Allah is the Arabic word for God. And if Christ died for all, do you think God only grants the gift to perform miracles, to just RC and EO saints?):
I have asked Shaykh why he does not let people know that he can do these things.
His reply is always “I can’t do anything. If Allah wishes for something to happen, then it does. If I think that I can do anything else it is my Nafs talking, and if I say I can do this or do that, then I am saying that “I” have power, which is not true. Only Allah has power, only Allah can"Do”. To think anything else is saying that Allah has a partner."
Perhaps this is the biggest miracle of all.
Or to quote form a story of science (see Phrase Origins: What do people mean when they say “it’s turtles all the way down”?).
A well-known scientist (some say it was Bertrand Russell) once gave a public lecture on astronomy. He described how the earth orbits around the sun and how the sun, in turn, orbits around the center of a vast collection of stars called our galaxy. At the end of the lecture, a little old lady at the back of the room got up and said: “What you have told us is rubbish. The world is really a flat plate supported on the back of a giant tortoise.” The scientist gave a superior smile before replying, “What is the tortoise standing on?” “You’re very clever, young man, very clever”, said the old lady. “But it’s turtles all the way down!”
Hypothetically, one could embrace John Calvin theologically and Arthur Schopenhauer philosophically - and be immensely happy. I really would have no idea why. But it is very possible