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.