You can't derive an 'ought' from an 'is'.
Hume's 1739 observation that writers slide from statements about what is to statements about what ought to be without noticing. No factual finding alone settles a policy question, which is why "the science says" is always incomplete.
In practice
- A study showing a policy reduces harm does not establish that the policy should be adopted, because that requires a view about what else is worth giving up.
- A finding that a group performs differently on a measure carries no conclusion about what anyone is owed, and treating it as one skips the step.