Beyond Convenience: A Case and Method for Purposive Sampling in Chemistry Teacher Professional Development Research

When
designing a study, the sampling method for selecting research
participants is an important decision with a host of considerations.
When designing a professional development (PD) program with a limited
number of spaces, the method of choosing participants from the applicants
is also important. When research and professional development are
entwined, sets of sampling criteria could conflict. Additionally,
in a mixed methods study, such as the one undertaken by the researchers,
additional trade-offs exist when considering the many potential methods
of sampling and participant selection. In this report, we present
a novel solution to the problem of multiple-criterion-focused selection
of research and PD participants when the number of applicants to participate
outnumbers the availability of resources. By using a weighted ranking
system, we were able to incorporate multiple purposive sampling criteria
in a simultaneous, rather than sequential, fashion. This allowed us
to focus our evaluation of chemistry-specific free-response questions
on a narrower pool of finalists and more consistently rate their responses.
This multipurposive sampling method and a novel tool developed herein
have broad implications for both sampling for chemistry education
research and participant selection in professional development.