[jeffreyH (OP)]

Most people have likely heard about clinical trials. What people are less likely to know are the guidelines for clinical trials. Is there a set methodology that can be used? Or does this depend upon what the trial is trying to determine?

[Bored chemist]

Or does this depend upon what the trial is trying to determine?

How could it not depend on that?

[jeffreyH (OP)]

It could be a badly formulated clinical trial.

[RD]

... clinical trials.... Is there a set methodology that can be used?

RCT is the gold-standard ... https://en.wikipedia.org/wiki/Randomized_controlled_trial

[Bored chemist]

It could be a badly formulated clinical trial.

It could.
Why would someone waste money on a badly built trial?
Well, I guess one answer would be "to get the result they wanted".
To do that, they would need to "rig" the trial.
In which case this would still apply
"Or does this depend upon what the trial is trying to determine?".

No trial that took place without oversight from an ethics committee would get published in any reputable journal or used as evidence by any competent individual or organisation.

Ethics committees ensure that the rights of the experimental subjects are protected.
One such right is that they are not used in "pointless" trials. It's unethical to (for example) stick a needle in someone unless there is some sort of benefit to society.

On the other hand it's all too common for a trial to be done, get the "wrong" result and not get published.

[evan_au]

You sometimes hear about "Phase 1 trials" in healthy volunteers - they are not testing the effectiveness against the disease, but seeing whether it is dangerous in some unexpected way. Trials can then proceed to Phase 2, 3 etc.
- Unfortunately, the whole process costs billions of dollars to bring a new medicine to market.
See: https://en.wikipedia.org/wiki/Clinical_trial#Phases

This cost is unreasonable for diseases for which there is no known treatment - especially if they afflict countries that can't pay for the development, or affect a very small percentage of the population. So a quicker development path has been approved for these treatments.
https://en.wikipedia.org/wiki/Orphan_drug

If a medical procedure is a diagnostic test, conducted outside the human body (eg for blood pressure, diabetes or genetic susceptibility), it can have a much shorter approval cycle, because you aren't injecting some foreign chemical into the patient's body. You just have the risk that the person drawing the blood sample will slip - a known and acceptable risk.