Scaling Office Hours: Managing Live Q&A in Large Courses

Computer Science 50 (CS50) is Harvard University’s introductory course for majors and nonmajors alike. So that students have an adequate support structure with which to tackle the course’s weekly programming assignments, we offer weekly “office hours,” during which students can receive one-on-one help from teaching assistants. In Fall 2010 and years prior, office hours were held in a basement-level computer lab. However, this environment did not appeal to staff or students. Moreover, this format for office hours suffered from logistical inefficiencies, repetition of questions among students, and lack of communication among staff, which led to high wait times for students. We relocated office hours in Fall 2011 to dining halls to create a more social and collaborative workspace, with more staff on duty at once. We also developed CS50 Queue, a web- and iPadbased system for managing office hours’ logistics. Overall, the new format proved a success. Attendance at office hours grew more than linearly, with an average of 120 students attending per night, up from 30 students in 2010 despite only a 23% increase in enrollment. Even though Queue enabled us to scale, new logistical challenges arose, and wait times for students still sometimes exceeded an hour. We intend to address those challenges in Fall 2012 in order to reduce wait times to 15 minutes at most.Engineering and Applied Science

Streamlining Grading toward Better Feedback

CS50 is Harvard University's introductory course aimed at majors and non-majors alike. Each week, students complete programming assignments and have traditionally received feedback from staff in the form of comments on PDFs of their code. Staff have historically reported spending significant amounts of time grading because of bottlenecks that included generating PDF documents and manually emailing feedback to students. Because we preferred that staff spend less of their time on grading logistics and more time providing feedback and helping students online or in person, we set out to improve the efficiency of the grading process. In Fall 2012, we developed and deployed CS50 Submit, a web-based utility through which staff can leave feedback for students via inline "sticky notes." Following the introduction of CS50 Submit, staff reported grading for 10% fewer hours (i.e., 42 minutes) per week and 13% fewer minutes (i.e., 4 minutes) per student, even while providing as much or more feedback. Meanwhile, we observed significantly higher levels of engagement with the course's online discussion board among staff, suggesting a more favorable distribution of staff workload. With CS50 Submit, we have also been able to audit exactly how much time staff spent grading each week in order to identify additional bottlenecks. Using CS50 Submit, we also observed that, on average, 9% of students each week never read their graders' comments, with a peak one week of 14%. The number of students who did not read feedback increased with time, which has led us to question whether asynchronous, textual comments are the most effective feedback mechanisms for students. In future terms, we plan to experiment with in-person, interactive means of delivering feedback to students. In this paper, we present CS50 Submit and the insights it has yielded into the behavior of students and staff alike.Engineering and Applied Science

Engaging Students through Video: Integrating Assessment and Instrumentation

CS50 is Harvard’s introductory course for majors and non-majors alike. For years, we have posted videos of the course’s lectures and sections online for the sake of review and distance education alike. But students’ experience with these videos has been historically passive. Students have been able to watch the course’s content on demand, rewinding and fast-forwarding at will, but they have not had means to engage interactively with the content or to check their understanding of material while watching videos. Furthermore, while we collected basic usage data (e.g., how many times a video was viewed), we lacked detailed analytics describing, for example, which portions of a video were commonly skipped or watched multiple times by students. To make videos more immersive and engaging for students, we developed CS50 Video, an open-source video player for desktop and mobile devices. CS50 Video allows instructors to integrate assessment questions to be answered by students at their own pace or at specific points in time directly into a video player. CS50 Video also allows students to search over video transcripts to find content easily as well as view videos at variable playback speeds (in order to make videos more accessible for ESL learners). Finally, CS50 Video integrates with third-party analytics solutions to allow instructors to view detailed usage statistics describing how students are interacting with videos (e.g., which videos or portions of videos are commonly watched or skipped over). We have deployed CS50 Video to students taking CS50 online and have obtained preliminary results. Because CS50 Video stores responses to questions server-side, we have been able to track students’ performance on in-video assessments. Thus far, we have observed that only 28% of students who watch online videos have engaged with assessment questions. Students who answer an assessment question incorrectly on their first attempt will often try again until reaching a correct answer, with 84.5% of correct answers reached in at most three attempts. We next plan to analyze the effects of in-video assessments on students’ mastery of material and introduce A/B-testing functionality for questions. We also plan to use students’ performance on assessments to understand the topics with which students struggle.Engineering and Applied Science

Redesigning Primary Care Processes to Improve the Offering of Mammography. The use of Clinic Protocols by Nonphysicians.

OBJECTIVE: To develop, within the framework of continuous quality improvement, new processes for offering mammography and determine whether protocols executed completely by nonphysicians would increase mammography utilization. DESIGN: A prospective follow-up study with patients from an intervention clinic and two control clinics. SETTING: Three general internal medicine clinics in a large, urban teaching hospital in Detroit, Michigan. PATIENTS/PARTICIPANTS: A total of 5,934 women, aged 40 through 75 years, making 16,546 visits to one of the clinics during the study period (September 1, 1992, through November 31, 1993). INTERVENTION: Medical assistants and licensed practical nurses in the intervention clinic were trained to identify women due for screening mammography, and to directly offer and order a mammogram if patients agreed. MEASUREMENTS AND MAIN RESULTS: Patients were considered up-to-date with screening if they had a mammogram within 1 year (if age 50-75) or 2 years (if age 40-49) prior to the visit or a mammogram within 60 days after the visit. The proportion of visits each month in which a woman was up-to-date with mammography was calculated using computerized billing records. Prior to the intervention, the proportion of visits in which women were up-to-date was 68% (95% confidence interval [CI] 63%, 73%) in the intervention clinic and 66% (95% CI 61%, 71%) in each of the control clinics. At the end of the evaluation, there was an absolute increase of 9% (95% CI 2%, 16%) in the intervention clinic, and a difference of 1% (95% CI -5%, 7%) in one of the control clinics and -2% (95% CI -3%, 5%) in the other. In the intervention clinic, the proportion of visits in which women were up-to-date with mammography increased over time and was consistent with a linear trend (p = .004). CONCLUSIONS: Redesigning clinic processes to make offering of mammography by medical assistants and licensed practical nurses a routine part of the clinic encounter can lead to mammography rates that are superior to those seen in physicians\u27 usual practice, even when screening levels are already fairly high. Physicians need not be considered the sole, or even the primary, member of the health care team who can effectively deliver some preventive health measures

The Parity Bit in Quantum Cryptography

An $n$-bit string is encoded as a sequence of non-orthogonal quantum states. The parity bit of that $n$-bit string is described by one of two density matrices, $\rho_0^{(n)}$ and $\rho_1^{(n)}$, both in a Hilbert space of dimension $2^n$. In order to derive the parity bit the receiver must distinguish between the two density matrices, e.g., in terms of optimal mutual information. In this paper we find the measurement which provides the optimal mutual information about the parity bit and calculate that information. We prove that this information decreases exponentially with the length of the string in the case where the single bit states are almost fully overlapping. We believe this result will be useful in proving the ultimate security of quantum crytography in the presence of noise.Comment: 19 pages, RevTe

A review of symptomatic leg length inequality following total hip arthroplasty

Leg length inequality (LLI) following total hip replacement is a complication which features increasingly in the recent literature. The definition of LLI is complicated by lack of consensus regarding radiological measurement, clinical measurement and the incomplete relationship between LLI and associated symptoms. This paper reviews 79 reports relating to LLI post hip replacement, detailing definitions and classification and highlighting patient populations prone to symptomatic LLI. While there is no universal definition of LLI, there is a broad consensus that less than 10 mm of difference on AP view plain radiographs is clinically acceptable. There are few techniques described that consistently produce a postoperative LLI of less than this magnitude. Where postoperative LLI exists, lengthening appears to cause more problems than shortening. In cases of mild LLI, non-surgical management produces adequate outcomes in the majority of cases, with functional LLI cases doing better than those with true LLI. Operative correction is effective in half of cases, even where nerve palsy is present, and remains an important option of last resort. Poor outcomes in patients with LLI may be minimised if individuals at risk are identified and counselled appropriately