  Case-oriented physics education research - which seeks to refine and develop
theory by linking that theory to cases - incorporates distinct practices for
selecting data for analysis, generalizing results, and making causal claims.
Unanswered questions about these practices may constrain researchers more
familiar with the recurrence-oriented research paradigm - which seeks to inform
instructional predictions by discerning reproducible, representative patterns
and relationships - from participating in or critically engaging with
case-oriented research. We use results from interviews with physics education
researchers, a synthesis of the literature on research methodologies, and
published examples of case-oriented and recurrence-oriented research to answer
"hard-hitting questions" that researchers may pose. In doing so, we aim to
substantiate our position that both case-oriented and recurrence- oriented PER
are rigorous but that the rigor is of a different nature in each paradigm.
