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

Atomic spectroscopy on a chip

Abstract: We demonstrate the ability to generate extremely large rubidium densities in uncoated hollow-core photonic band-gap fibers using lightinduced atomic desorption. Once the fiber is exposed to Rb vapor for 1-2 weeks, and this atomic source is removed, the fiber yields large desorbable densities for an extended period of time. We show that optical depths greater than e -1200 can be created within seconds. Our observed Rb densities are several orders of magnitude larger than any previously reported to be generated optically, and allow for the demonstration of a relatively easy-touse fiber-based vapor cell capable of producing large optical depths without the need for thermal tuning. H. Schmidt and A. Imamoğlu, "Giant Kerr nonlinearities obtained by electromagnetically-induced transparency," Opt. Lett. 21, 1936Lett. 21, -1938Lett. 21, (199

The Integrated Testlet: A powerful multiple-choice approach for STEM assessment.

Multiple-choice testing is becoming more common as student populations rise and instructional resources dwindle. Such testing is easy to implement, reliable, and inexpensive, yet its validity is often in question (Scott, Stelzer, & Gladding, 2006). In an effort to find inexpensive, streamlined, and valid ways to test knowledge integration and deeper levels of understanding we have introduced integrated testlets which complement recent extensions of the traditional multiple-choice approach (e.g. Ding, Reay, Lee, & Bao, 2011; and Wilcox & Pollock, 2014). Integrated testlets efficiently assess higher echelons of learning by utilizing answer-until-correct assessment tools within a set of multiple choice questions that share a common scenario and which build upon one another. These also allow for straightforward and demonstrably-valid granting of partial credit. Integrated testlets enable conceptual scaffolding to be tested and, if desired, assembled during the assessment. Thus, they serve both summative and formative purposes. In this workshop we will introduce examples of integrated testlets that span the STEM disciplines. Participants will actively engage with one or two testlets of their choosing to gain experience with both the technology and the workings of this assessment tool. Time will then be devoted to unpacking these experiences and to highlighting the pedagogical implications of being able to assess integration of knowledge within a multiple-choice framework. Finally we will discuss how integrated testlets are currently transforming students’ learning experiences at Trent University. Wilcox, B.R., & Pollock, S. J. (2014). Coupled multiple-response versus free-response conceptual assessment: An example from upper-division physics. Physical Review Special Topics - Physics Education Research, 10(2), 020124-1 – 020124-11. http://dx.doi.org/10.1103/physrevstper.10.020124 Ding, L., Reay, N., Lee, A., & Bao, L. (2009). Exploring the role of conceptual scaffolding in solving synthesis problems. Physical Review Special Topics - Physics Education Research, 7(2), 020109-1 – 020109-11. http://dx.doi.org/10.1103/physrevstper.7.020109 Scott, M., Stelzer, T., & Gladding, G. (2009). Evaluating multiple-choice exams in large introductory physics courses. Physical Review Special Topics - Physics Education Research, 2(2), 020102-1 – 020102-14. http://dx.doi.org/10.1103/physrevstper.7.02010

Mimicking Multimodal Contrast with Vertex Component Analysis of Hyperspectral CARS Images

We show the applicability of vertex component analysis (VCA) of hyperspectral CARS images in generating a similar contrast profile to that obtained in “multimodal imaging” that uses signals from three separate nonlinear optical techniques. Using an atherosclerotic rabbit aorta test image, we show that the VCA algorithm provides pseudocolor contrast that is comparable to multimodal imaging, thus suggesting that under certain conditions much of the information gleaned from a multimodal nonlinear optical approach can be sufficiently extracted from the CARS hyperspectral stack itself. This is useful for unsupervised contrast generation on hyperspectral CARS implementations such as multiplex CARS that may not have multimodal capabilities. The utility of VCA as a quantitative analysis tool in CARS is also addressed

In vivo hyperspectral CARS and FWM microscopy of carotenoid accumulation in H. pluvialis

Coherent anti-Stokes Raman scattering (CARS) and four-wave-mixing (FWM) microscopy are a related pair of powerful nonlinear optical characterization tools. These techniques often yield strong signals from concentrated samples, but because of their quadratic dependence on concentration, they are not typically employed for imaging or identifying dilute cellular constituents. We report here that, depending on the excitation wavelengths employed, both CARS and degenerate-FWM signals from carotenoid accumulations in alga cysts can be exceptionally large, allowing for low-power imaging of astaxanthin (AXN) deposits in Haematococcus pluvialis microalga. By use of a broadband laser pulse scheme for CARS and FWM, we are able to simultaneously collect strong intrinsic two-photon-excitation fluorescence signals from cellular chlorophyll in vivo. We show that CARS signals from astaxanthin (AXN) samples in vitro strictly follow the expected quadratic dependence on concentration, and we demonstrate the collection of wellresolved CARS spectra in the fingerprint region with sensitivity below 2mM. We suggest that multimodal nonlinear optical microscopy is sufficiently sensitive to AXN and chlorophyll concentrations that it will allow for non-invasive monitoring of carotenogenesis in live H. pluvialis microalgae.Peer reviewed: YesNRC publication: Ye

Label-free hyperspectral nonlinear optical microscopy of the biofuel micro-algae Haematococcus Pluvialis

We consider multi-modal four-wave mixing microscopies to be ideal tools for the in vivo study of carotenoid distributions within the important biofuel microalgae Haematococcus pluvialis. We show that hyperspectral coherent anti-Stokes Raman scattering (CARS) microscopy generates non-invasive, quantitative real-time concentrations maps of intracellular carotenoid distributions in live algae.Peer reviewed: YesNRC publication: Ye

Microwave induced mechanical activation of hydrogel dimers

When grape-sized aqueous dimers are irradiated in a microwave oven, an intense electromagnetic hotspot forms at their point of contact, often igniting a plasma. Here we show that this irradiation can result in the injection of mechanical energy. By examining irradiated hydrogel dimers through high-speed imaging, we find that they repeatedly bounce off of each other while irradiated. We determine that an average of 1 lJ of mechanical energy is injected into the pair during each collision. Furthermore, a characteristic high-pitched audio signal is found to accompany each collision. We show that both the audio signal and the energy injection arise via an interplay between vaporization and elastic deformations in the region of contact, the so-called ‘elastic Liedenfrost effect’. Our results establish a novel, non-contact method of injecting mechanical energy into soft matter systems, suggesting application in fields such as soft robotics