When instructors provide time for students to discuss their ideas in Peer Instruction, instructors minimally expect that the conversation partners will discuss their opinions relating to the physical attributes posed in a question and submit clicker responses that coincide with individual opinions. We defined conversations that met these two criteria as "standard conversations." In our study of 361 recorded Peer Instruction conversations from large introductory astronomy classrooms taught by experienced instructors, we found that 38% of student conversations were standard conversations. Of the remaining 62%, we identified three broad categories consisting of ten types of "nonstandard" conversations. The first category of conversations describes student ideas that were not reflected in any of the given multiple choice answers. The second category includes issues related to the interpretation of the statistical feedback provided by electronic classroom response systems. The third category describes common pitfalls experienced by students during conversations that led to unproductive interactions. Our analysis of nonstandard Peer Instruction conversations will be useful to practitioners and researchers seeking to improve the implementation of Peer Instruction.

In 1995, Huffman and Heller used exploratory factor analysis to draw into question the factors of the Force Concept Inventory (FCI). Since then several papers have been published examining the factors of the FCI on larger sets of student responses and understandable factors were extracted as a result. However, none of these proposed factor models have been verified to not be unique to their original sample through the use of independent sets of data. This paper seeks to confirm the factor models proposed by Scott et al. in 2012, andHestenes et al. in 1992, as well as another expert model proposed within this study through the use of confirmatory factor analysis (CFA) and a sample of 20 822 postinstruction student responses to the FCI. Upon application of CFA using the full sample, all three models were found to fit the data with acceptable global fit statistics. However, when CFA was performed using these models on smaller sample sizes the models proposed by Scott et al. and Eaton and Willoughby were found to be far more stable than the model proposed by Hestenes et al. The goodness of fit of these models to the data suggests that the FCI can be scored on factors that are not unique to a single class. These scores could then be used to comment on how instruction methods effect the performance of students along a single factor and more in-depth analyses of curriculum changes may be possible as a result.

Twenty-four free-response questions were developed to explore introductory college astronomy students' understanding of gravity in a variety of contexts, including in and around Earth, throughout the solar system, and in hypothetical situations. Questions were separated into three questionnaires, each of which was given to a section of introductory college astronomy with 143, 137, and 32 respondents, respectively. Combined with 15 interviews, the exploratory, open-response format allowed themes to emerge naturally, with both documented and undocumented misconceptions observed. The breadth of questions allowed for descriptions of possible student mental frameworks, including alternative models and misapplication of the scientific model.

To investigate differences in learning gains by gender, we collected data in large introductory astronomy and biology courses. Male astronomy students had significantly higher pre-and post-test scores than female students on the astronomy diagnostic test. Male students also had significantly higher pretest and somewhat higher post-test scores than female students on a survey instrument designed for an introductory biology course. For both courses, males had higher learning gains than female students only when the normalized gain measure was utilized. No differences were found with any other measures, including other gain calculations, overall course grades, or individual exams. Implications for using different learning gain measures in science classrooms, as well as for research on learning differences by gender are discussed.

The study described here extends the applicability of the Newtonian Gravity Concept Inventory (NGCI) to college algebra-based physics classes, beyond the general education astronomy courses for which it was originally developed. The four conceptual domains probed by the NGCI (Directionality, Force Law, Independence of Other Forces, and Threshold) are well suited for investigating students' reasoning about gravity in both populations, making the NGCI a highly versatile instrument. Classical test theory statistical analysis with physics student responses preinstruction (N ¼ 1,392) and post-instruction (N ¼ 929) from eight colleges and universities across the United States indicate that the NGCI is composed of items with appropriate difficulty and discrimination and is reliable for this population. Also, expert review and student interviews support the NGCI's validity for the physics population. Emergent similarities and differences in how physics students reason about gravity compared to astronomy students are discussed, as well as future directions for analyzing the instrument's item parameters across both populations. V C 2016 American Association of Physics Teachers.