NSES Content Standard A  Science as Inquiry: Understanding about scientific inquiry  Grades K-4, page 123  Scientists develop explanations using observations (evidence) and what they already know about the world (scientific knowledge). Good explanations are based on evidence from investigations.

 
Benchmark 1B The Nature of Science: Scientific Inquiry
Grades 3-5, page 11
Scientists' explanations about what happens in the world come partly from what they observe, partly from what they think. Sometimes scientists have different explanations for the same set of observations. That usually leads to their making more observations to resolve the differences.

Benchmark 1B The Nature of Science: Scientific Inquiry
Grades 3-5, page 11
Scientists do not pay much attention to claims about how something they know about works unless the claims are backed up with evidence that can be confirmed and with a logical argument.