Integrated Testlets and the Immediate Feedback Assessment Technique

The increased use of multiple-choice (MC) questions in introductory-level physics final exams is largely hindered by reservations about its ability to test the broad cognitive domain that is routinely accessed with typical constructed-response (CR) questions. Thus, there is a need to explore ways in which MC questions can be utilized pedagogically more like CR questions while maintaining their attendant procedural advantages. we describe how an answer-until-correct MC response format allows for the construction of multiple-choice examinations designed to operate much as a hybrid between standard MC and CR testing. With this tool - the immediate feedback assessment technique (IF-AT) - students gain complete knowledge of the correct answer for each question during the examination, and can use such information for solving subsequent test items. This feature allows for the creation of a new type of context-dependent item sets; the "integrated testlet". In an integrated testlet certain items are purposefully inter-dependent and are thus presented in a particular order. Such integrated testlets represent a proxy of typical CR questions, but with a straightforward and uniform marking scheme that also allows for granting partial credit for proximal knowledge. We present a case study of an IF-AT-scored midterm and final examination for an introductory physics course, and discuss specific testlets with varying degrees of integration. In total, the items are found to allow for excellent discrimination, with a mean item-total correlation measure for the combined 45 items of the two examinations of $\bar{r}'=0.41\pm 0.13$ (mean $\pm$ standard deviation) and a final examination test reliability of $\alpha=0.82$ ($n=25$ items). Furthermore, partial credit is shown to be allocated in a discriminating and valid manner in these examinations.Comment: 13 pages. 7 figures. Accepted to the American Journal of Physics (August 2013

A comparison of integrated testlet and constructed-response question formats

Constructed-response (CR) questions are a mainstay of introductory physics textbooks and exams. However, because of time, cost, and scoring reliability constraints associated with this format, CR questions are being increasingly replaced by multiple-choice (MC) questions in formal exams. The integrated testlet (IT) is a recently-developed question structure designed to provide a proxy of the pedagogical advantages of CR questions while procedurally functioning as set of MC questions. ITs utilize an answer-until-correct response format that provides immediate confirmatory or corrective feedback, and they thus allow not only for the granting of partial credit in cases of initially incorrect reasoning, but furthermore the ability to build cumulative question structures. Here, we report on a study that directly compares the functionality of ITs and CR questions in introductory physics exams. To do this, CR questions were converted to concept-equivalent ITs, and both sets of questions were deployed in midterm and final exams. We find that both question types provide adequate discrimination between stronger and weaker students, with CR questions discriminating slightly better than the ITs. Meanwhile, an analysis of inter-rater scoring of the CR questions raises serious concerns about the reliability of the granting of partial credit when this traditional assessment technique is used in a realistic (but non optimized) setting. Furthermore, we show evidence that partial credit is granted in a valid manner in the ITs. Thus, together with consideration of the vastly reduced costs of administering IT-based examinations compared to CR-based examinations, our findings indicate that ITs are viable replacements for CR questions in formal examinations where it is desirable to both assess concept integration and to reward partial knowledge, while efficiently scoring examinations.Comment: 14 pages, 3 figures, with appendix. Accepted for publication in PRST-PER (August 2014

Teacher professional growth in an authentic learning environment

The last several decades have been marked by tremendous changes in education - technological, pedagogical, administrative, and social. These changes have led to considerable increments in the budgets devoted to professional development for teachers ~ with the express purpose of helping them accommodate their practices to the new realities oftheir classrooms. However, research has suggested that, in spite of the emphasis placed on encouraging sustained change in teaching practices, little has been accomplished. This begs the question of what ought to be done to not only reverse this outcome, but contribute to transformational change. The literature suggests some possibilities including: a) considering teachers as learners and applying what, is known about cognition and learning; b) modifying the location and nature ofprofessional development so that it is authentic, based in the classroom and focusing on tasks meaningful to the teacher; c) attending to the infrastructure underlying professional development; and d) ensuring opportunities for reflective practice. This dissertation looks at the impact of each ofthese variables through an analysis ofthe learning journeys of a group ofteachers engaged in a program called GrassRoots in one midsized school board in Ontario. Action research was conducted by the researcher in his role as consultant facilitating teacher professional growth around the use of Web sites as culminating performance tasks by students. Research focused on the pedagogical approach to the learning of the teachers involved and the infrastructure underlying their learning. Using grounded theory, a model for professional development was developed that can be used in the future to inform practices and, hopefully, lead to sustained transformational school change

Far-off resonance conditional phase-shifter using the ac-Stark shift

We propose a simple technique that achieves a conditional phase shift of pi radians between two weak lasers with energies at the 1000-photon level. The key idea is to set up a V-system with two far-off resonant lasers by coupling the ground state to two excited electronic states. The lasers interact through the ac Stark shift of the ground state and thereby acquire a large conditional phase shift.Comment: 4 pages, 3 figure

Monte Carlo Studies of the Intrinsic Second Hyperpolarizability

The hyperpolarizability has been extensively studied to identify universal properties when it is near the fundamental limit. Here, we employ the Monte Carlo method to study the fundamental limit of the second hyperpolarizability. As was found for the hyperpolarizability, the largest values of the second hyperpolarizability approaches the calculated fundamental limit. The character of transition moments and energies of the energy eigenstates are investigated near the second hyperpolarizability's upper bounds using the missing state analysis, which assesses the role of each pair of states in their contribution. In agreement with the three-level ansatz, our results indicate that only three states (ground and two excited states) dominate when the second hyperpolarizability is near the limit.Comment: 8 pages, 7 figure

CARS and SHG microscopy to follow the collagen production in living human corneal fibroblasts and mesenchymal stem cells in fibrin gel 3D cultures

Coherent anti-Stokes Raman scattering (CARS) microscopy is combined with second harmonic generation (SHG) technique in order to follow the early stage of stem cell differentiation within a 3D scaffold. CARS microscopy can detect lipid membranes and droplet compartments in living cells and SHG microscopy enables a strong imaging contrast for molecules with a non-centrosymmetric ordered structure like collagen. One of the first evidence of hMSCs differentiation is the formation of an extracellular matrix (ECM) where the collagen protein is its main component. This work demonstrated the multimodal CARS and SHG microscopy as a powerful non-invasive label free technique to investigate the collagen production dynamic in living cell 3D cultures. Its ability to image the cell morphology and the produced collagen distribution on a long term (4 weeks) experiment allowed to obtain important information about the cell-scaffold interaction and the ECM production. The very low limit reached in detecting collagen has permitted to map even the small amount of collagen produced by the cells in few hours of culture. This demonstrates multimodal CARS and SHG microscopy as a novel method to follow cells collagen production and cells differentiation process. In addition the experiment shows that the technique is a powerful tool for imaging of very thick sections (about 4 mm). The study conducted on mesenchymal stem cell in fibrin gel cultures confirmed that differentiation stimulus is induced by the scaffold. The monitoring of stem cell differentiation within a scaffold in a non-destructive way will be an important advantage in regenerative medicine and tissue engineering field.Comment: 15 pages, 5 figures, ECONOS 201