Academic Appointments

2023-24 Courses

All Publications

  • Spatial clustering of hookah lounges, vape shops and all tobacco retailers near colleges. Nicotine & tobacco research : official journal of the Society for Research on Nicotine and Tobacco Sun, D. L., Schleicher, N. C., Recinos, A., Henriksen, L. 1800


    BACKGROUND: US college students smoke hookah and vape nicotine at higher rates than other young adults. Density/proximity of hookah lounges and vape shops near colleges has been described, but this study is the first to test whether tobacco retailers spatially cluster near college campuses.METHODS: We created and linked spatial shapefiles for community colleges and 4-year universities/colleges in California with lists of hookah lounges, vape shops and licensed tobacco retailers. We simulated 100 data sets, placing hookah lounges, vape shops and tobacco retailers randomly in census tracts in proportion to population density. A modified version of Ripley's K-function was computed using the radius (r) from each retailer within retail category.RESULTS: In 2018/2019, 50.5% of hookah lounges (n=479), 42.5% of vape shops (n=2,467) and 42.0% of all tobacco retailers (n=31,100) were located within 3 miles of a community college. Spatial clustering was significant (p<0.05) from at least 0.4 miles for hookah lounges, 0.1 mile for vape shops, and 0.3 miles for all tobacco retailers. For 4-year universities/colleges, approximately 46.8% of hookah lounges, 31.3% of vape shops and 31.6% of all tobacco retailers were located within 3 miles. Clustering was significant from 0.2 miles for hookah lounges and 1.3 miles for all tobacco retailers but was not significant for vape shops.CONCLUSION: Evidence that some types of tobacco retailers cluster near community colleges and 4-year universities/colleges implies greater accessibility and exposure to advertising for students. It is also concerning because a higher probability of underage tobacco sales presumably exists near colleges.IMPLICATIONS: Prior studies infer that hookah lounges and vape shops cluster near colleges from the density and closer proximity to campuses. This study modified a traditional test of spatial clustering and considered community colleges separately from 4-year universities. Spatial clustering of hookah lounges and all licensed tobacco retailers was evident near both types of campuses, but vape shops clustered only near community colleges. Place-based strategies to limit tobacco retail density could expand state/local laws that prohibit tobacco sales near schools to include retailers near college campuses. In addition, college environments should be a target for reducing hookah smoking and nicotine vaping.

    View details for DOI 10.1093/ntr/ntac007

    View details for PubMedID 35022769

  • Empirical Bayes Mean Estimation With Nonparametric Errors Via Order Statistic Regression on Replicated Data JOURNAL OF THE AMERICAN STATISTICAL ASSOCIATION Ignatiadis, N., Saha, S., Sun, D. L., Muralidharan, O. 2021
  • Neighborhood variation in the price of cheap tobacco products in California: Results from Healthy Stores for a Healthy Community. Nicotine & tobacco research Henriksen, L., Andersen-Rodgers, E., Zhang, X., Roeseler, A., Sun, D. L., Johnson, T. O., Schleicher, N. C. 2017


    Retail marketing surveillance research highlights concerns about lower-priced cigarettes in neighborhoods with a higher proportion of racial/ethnic minorities, but focuses almost exclusively on premium brands. To remedy this gap in the literature, the current study examines neighborhood variation in prices for the cheapest cigarettes and a popular brand of cigarillos in a large statewide sample of licensed tobacco retailers in a low-tax state.All 61 local health departments in California trained data collectors to conduct observations in a census of eligible licensed tobacco retailers in randomly selected zip codes (n=7,393 stores, completion rate=91%). Data were collected in 2013, when California had a low and stagnant tobacco tax. Two prices were requested: the cheapest cigarette pack regardless of brand and a single, flavored Swisher Sweets cigarillo. Multilevel models (stores clustered in tracts) examined prices (before sales tax) as a function of neighborhood race/ethnicity and proportion of school-age youth (ages 5-17). Models adjusted for store type and median household income.Approximately 84% of stores sold cigarettes for less than $5 and a Swisher Sweets cigarillo was available for less than $1 in 74% of stores that sold the brand. The cheapest cigarettes cost even less in neighborhoods with a higher proportion of school-age residents and Asian/Pacific Islanders.Neighborhood disparities in the price of the cheapest combustible tobacco products are a public health threat. Policy changes that make all tobacco products, especially combustible products, less available and more costly may reduce disparities in their use and protect public health.Much of what is known about neighborhood variation in the price of combustible tobacco products focuses on premium brand cigarettes. The current study extends this literature in two ways, by studying prices for the cheapest cigarette pack regardless of brand and a popular brand of flavored cigarillos, and by reporting data from the largest statewide sample of licensed tobacco retailers. Significantly lower prices in neighborhoods with a higher proportion of youth and of racial/ethnic groups with higher smoking prevalence are a cause of concern. The study results underscore the need for policies that reduce availability and increase price of combustible tobacco products, particularly in states with low, stagnant tobacco taxes.

    View details for DOI 10.1093/ntr/ntx089

    View details for PubMedID 28444233

  • Inequalities in tobacco outlet density by race, ethnicity and socioeconomic status, 2012, USA: results from the ASPiRE Study. Journal of epidemiology and community health Lee, J. G., Sun, D. L., Schleicher, N. M., Ribisl, K. M., Luke, D. A., Henriksen, L. 2017


    Evidence of racial/ethnic inequalities in tobacco outlet density is limited by: (1) reliance on studies from single counties or states, (2) limited attention to spatial dependence, and (3) an unclear theory-based relationship between neighbourhood composition and tobacco outlet density.In 97 counties from the contiguous USA, we calculated the 2012 density of likely tobacco outlets (N=90 407), defined as tobacco outlets per 1000 population in census tracts (n=17 667). We used 2 spatial regression techniques, (1) a spatial errors approach in GeoDa software and (2) fitting a covariance function to the errors using a distance matrix of all tract centroids. We examined density as a function of race, ethnicity, income and 2 indicators identified from city planning literature to indicate neighbourhood stability (vacant housing, renter-occupied housing).The average density was 1.3 tobacco outlets per 1000 persons. Both spatial regression approaches yielded similar results. In unadjusted models, tobacco outlet density was positively associated with the proportion of black residents and negatively associated with the proportion of Asian residents, white residents and median household income. There was no association with the proportion of Hispanic residents. Indicators of neighbourhood stability explained the disproportionate density associated with black residential composition, but inequalities by income persisted in multivariable models.Data from a large sample of US counties and results from 2 techniques to address spatial dependence strengthen evidence of inequalities in tobacco outlet density by race and income. Further research is needed to understand the underlying mechanisms in order to strengthen interventions.

    View details for DOI 10.1136/jech-2016-208475

    View details for PubMedID 28249990


    View details for DOI 10.1214/15-AOS1371

    View details for Web of Science ID 000375175200001

  • Peer Assessment Enhances Student Learning: The Results of a Matched Randomized Crossover Experiment in a College Statistics Class PLOS ONE Sun, D. L., Harris, N., Walther, G., Baiocchi, M. 2015; 10 (12)


    Feedback has a powerful influence on learning, but it is also expensive to provide. In large classes it may even be impossible for instructors to provide individualized feedback. Peer assessment is one way to provide personalized feedback that scales to large classes. Besides these obvious logistical benefits, it has been conjectured that students also learn from the practice of peer assessment. However, this has never been conclusively demonstrated. Using an online educational platform that we developed, we conducted an in-class matched-set, randomized crossover experiment with high power to detect small effects. We establish that peer assessment causes a small but significant gain in student achievement. Our study also demonstrates the potential of web-based platforms to facilitate the design of high-quality experiments to identify small effects that were previously not detectable.

    View details for DOI 10.1371/journal.pone.0143177

    View details for PubMedID 26683053

    View details for PubMedCentralID PMC4684290

  • NON-NEGATIVE MATRIX COMPLETION FOR BANDWIDTH EXTENSION: A CONVEX OPTIMIZATION APPROACH 23rd IEEE International Workshop on Machine Learning for Signal Processing (MLSP) Sun, D. L., Mazumder, R. IEEE. 2013
  • UNIVERSAL SPEECH MODELS FOR SPEAKER INDEPENDENT SINGLE CHANNEL SOURCE SEPARATION IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP) Sun, D. L., Mysore, G. J. IEEE. 2013: 141–145
  • Speaker and Noise Independent Voice Activity Detection Germain, F. G., Sun, D. L., Mysore, G. J., Bimbot, F., Cerisara, C., Fougeron, C., Gravier, G., Lamel, L., Pellegrino, F., Perrier, P. ISCA-INT SPEECH COMMUNICATION ASSOC. 2013: 732-736