Here's a section from an explanation of the Daubert decision:
Scientific knowledge = scientific method/methodology: A conclusion will qualify as scientific knowledge if the proponent can demonstrate that it is the product of sound "scientific methodology" derived from the scientific method.
Factors relevant: The Court defined "scientific methodology" as the process of formulating hypotheses and then conducting experiments to prove or falsify the hypothesis, and provided a nondispositive, nonexclusive, "flexible" set of "general observations" (i.e. not a "test") that it considered relevant for establishing the "validity" of scientific testimony:
- Empirical testing: whether the theory or technique is falsifiable, refutable, and/or testable.
- Whether it has been subjected to peer review and publication.
- The known or potential error rate.
- The existence and maintenance of standards and controls concerning its operation.
- The degree to which the theory and technique is generally accepted by a relevant scientific community.