Liu Lan

bio

        刘岚教授 本科于中国科学技术大学毕业后,赴美国北卡罗来那大学教堂山分校 (University of North Carolina at Chapel Hill) 攻读生物统计专业,并于三年后获得博士学位。后赴美国哈佛大学生物统计和流行病系从事博士后研究。在美国明尼苏达大学获得长聘副教授,在首都医科大学获得教授。刘岚教授获得国家高层次人才引进项目。

        刘岚教授担任统计顶级期刊Journal of American Statistical Association副主编、医学期刊Journal of American Heart Association客座编辑,Stroke统计主编(statistical editor)。在统计和医学杂志发表论文30余篇,主导过五个国家级的研究项目(其中的一个在当年的NIH基金评审中排名前1%)。


        在统计应用上,刘岚教授在美国食品药品监管局(FDA)的CDER部门工作实习,参与了对于缺失数据指导方案前期的探索研究。 在美期间,刘岚教授与医学专家合作,进行实验设计和数据分析,论文发表在多个不同领域医学杂志。同时,刘岚教授和首都医科大学吉训明院士团队长期合作,深度参与了BAOCHE(已发表在NEJM上)、OPENS2, TREND(已发表在JAMA Neurology上), RICH2等大型研究的实验设计和统计分析。 此外,刘岚教授拥有丰富的统计咨询经验,与美国明尼苏达州财政部、劳工部、刑事犯罪局、纽约房屋管理局均有合作项目。


永远做重要的研究

        什么是重要的研究?首先,它是要能有影响力的,要么能改变人们对于食物的认知,从而改变medical practice(应用型),或者大家做研究的方式(方法学)。第二,它是要可信的,至少你对你的结果是有信心的。

        首先讨论影响力。研究是以研究为导向,而不是论文为导向的。一个研究是一个复杂的项目,研究的中间过程会产生论文。很多人会讨论SCI分区,对于我而言,如果一个研究一开始就是冲着二区的,那么这个研究不做也罢。所有的研究都应该是最终结果能发在一区,甚至是顶刊的。当然,研究过程中为了解决最终问题,会去解决一些小的问题(类似数学中的引理),这些小的步骤是可以作为论文发表在其他期刊上的。为了研究明白,早期我进行了一定摸索,其中会有一些很小的结果,灌水也可以发一区甚至顶刊,这种行为无可厚非,毕竟每个人处境不同,但是我不希望我的研究和我的学生走这条路。

        接下来讨论可信。有些学生有个不好的习惯,那就是对一个方法一知半解就改改代码就用了。我在作为统计编辑和审稿人的工作中见得很多,这种行为也很一目了然。所以我希望我的学生能充分理解他们所用的方法,只有这样,他们自己才可能相信自己做的研究。 我希望培养终身型的研究人员。如果不能够做重要的研究,只是为了职称和功利目的,这样的研究是持续不了的,一个人会burn out的。只有做重要的研究,这些研究非功利性的激励才能成为一个研究人员终身的动力。

Research and publishing

  • * indicates student

    † indicates corresponding author

    When I first started my PhD, I was involved in several projects involving vaccines (1-4). I was amazed ...

    When I first started my PhD, I was involved in several projects involving vaccines (1-4). I was amazed to learn that some vaccines like pneumococcal vaccine may have moderate protection on children receiving the vaccine, but they confer more significant protection on the elderly in the family. This cross-protection, is a form of interference, makes vaccine very useful, but also limits the scope of statistical analysis on vaccine. This motivated my theoretical research on statistical anlysis in the presence of interference (5-7).

    1.  S. Becker-Dreps, E. Amaya, L. Liu, G. Moreno, J. Rocha, R. Brice˜no, J. Alem´an, M.G. Hudgens, C.W. Woods, D.J. Weber, (2014) “Changes in Childhood Pneumonia and Infant Mortality Rates Following Introduction of the 13-valent Pneumococcal Conjugate Vaccine in Nicaragua”, The Pediatric Infectious Diseases Journal, 33(6):637-642.

    2.  S. Becker-Dreps, M. Mel´endez, L. Liu, L. E. Zambrana, M. Paniagua, D. J. Weber, M. G. Hudgens, M. C´aceres, R. Achi, C. K¨allest˚all, D. R. Morgan, F. Espinoza, R. Pe˜na, (2013) “Community Diarrhea Incidence Before and After Rotavirus Vaccine Introduction in Nicaragua”. The American Journal of Tropical Medicine and Hygiene, 89(2), 246-250.

    3.  S. Becker-Dreps, F. Bucardo, S. Vilchez, L. E. Zambrana, L. Liu, D. J. Weber, R. Pe˜na, L. Barclay, J. Vinj´e, M. G. Hudgens, J. Nordgren, L. Svensson, D. R. Morgan, F. Espinoza, M. Paniagua, (2014) “Etiology of Childhood Diarrhea Following Rotavirus Vaccine Introduction: A Prospective, Population-based Study in Nicaragua”. The Pediatric Infectious Disease Journal, 33(11), 1156-1163.

    4.  S. Becker-Dreps, E. Amaya, L. Liu, J. Rocha, R. Brice˜no, G. Moreno, J. Aleman, M. G. Hudgens, C. W. Woods, D. Weber, (2015) “Impact of a combined pediatric and adult pneumococcal immunization program on adult pneumonia incidence and mortality in Nicaragua”. Vaccine, 33(1), 222-227.

    5.  L. Liu, M. G. Hudgens, “Large Sample Randomization Inference of Causal Effects in the Presence of Interference”, (2014) Journal of the American Statistical Association (JASA) Theory and Methods Section, 109(505):288-301.

    7.  L. Liu†, M. G. Hudgens, B. Saul, J. Clemens, M. Ali, M. Emch (2018+) “Doubly Robust Estimation in Observational Studies with Interference”, Stat, 8, e214.

    8.  Liu, Lan, and Eric Tchetgen Tchetgen. "Regression‐based negative control of homophily in dyadic peer effect analysis." Biometrics 78, no. 2 (2022): 668-678.

  • * indicates student

    † indicates corresponding author

    I wrapped up my PhD to take a postdoctoral position with Eric Tchetgen Tchetgen. With the help of my advisor Michael ...

    I wrapped up my PhD to take a postdoctoral position with Eric Tchetgen Tchetgen. With the help of my advisor Michael Hudgens, I was lucky that I could find and work on a research topic so quickly. However, my PhD training was shorter than usual, so I needed to get exposed to more canonical research methodologies during my post-doc years. I mainly worked on semiparametric methods, in the context of doubly robust estimators, and instrumental variable.

    1.  B. Sun, L. Liu, J. M. Robins, E. Tchetgen Tchetgen (2018) “Doubly Robust Instrumental Variable Estimation in Missing not at Random Problems, Statistica Sinica, 28, 1965-1983.

    2.  L. Liu, W. Miao, B. Sun, J. M. Robins, E. Tchetgen Tchetgen (2020) “Instrumental Variable Estimation of the Marginal Effect of Treatment on the Treated, Statistica Sinica, 30, 1517-1541.

    3.  W. Li*, Y. Gu, L. Liu† (2020) “Demystifying a Class of Multiple Robust Estimators”, Biometrika, 207, 919-933.

    4.  Z. Sun*, L. Liu† “Semiparametric Inference with Missing Not at Random Confounders”, in press at Statistica Sinica.

    5.  Miao, Wang, Lan Liu, Yilin Li, Eric J. Tchetgen Tchetgen, and Zhi Geng. "Identification and semiparametric efficiency theory of nonignorable missing data with a shadow variable." ACM/JMS Journal of Data Science 1, no. 2 (2024): 1-23.

  • * indicates student

    † indicates corresponding author

    Surrogate outcome is used to substitute the real outcome we care about, if the real outcome ...

    Surrogate outcome is used to substitute the real outcome we care about, if the real outcome is costly to measure. For example, if cancer survival takes a long time to measure, we may use changes in tumor size as a surrogate outcome. However, sometimes results based on a surrogate could be misleading--an improvement in the surrogate outcome could happen when there is a deteriotion of the real outcome. This is so-called surrogate paradox. When this happens, the results are usually disastrous.

    1.  Y. Yin*, L. Liu†, Z. Geng, P. Luo (2020) “Novel criteria to exclude the surrogate.

    2.  paradox and their optimalities”, Scandinavian Journal of Statistics, 47, 84-103.

    3.  L. Ma*, Y. Yin*, L. Liu†, Z. Geng (2021) “On the Individual Surrogate Paradox”, Biostatistics, 22, 97-113.

    4.  Y. Yin*, L. Liu†, Z. Geng, (2018) “Assessing the Treatment Effect Heterogeneity.

    5.  with a Latent Variable”, Statistica Sinica, 28, 115-135.

  • * indicates student

    † indicates corresponding author

    When I was an assistant professor in University of Minneasota, I learned about a method of dimension ...

    When I was an assistant professor in University of Minneasota, I learned about a method of dimension reduction called envelope method from the very person who started this strand of research: Dennis Cook.

    1.  Y. Shi*, L. Ma*, L. Liu† “Efficient Regression in Mixed Effects Models”, (2020) Stat, doi: 10.1002/sta4.313.

    2.  L. Ma*, L. Liu†, Wei Y. “Envelope Methods with Ignorable Missing Data”, The Electronic Journal of Statistics, 15, 4420-4461.

    3.  Liu, Lan, Wei Li*†, Zhihua Su, Dennis Cook, Luca Vizioli, and Essa Yacoub. "Efficient estimation via envelope chain in magnetic resonance imaging‐based studies." Scandinavian Journal of Statistics 49, no. 2 (2022): 481-501.

    4.  Cook, R. Dennis, Liliana Forzani, and Lan Liu†. "Partial least squares for simultaneous reduction of response and predictor vectors in regression." Journal of Multivariate Analysis 196 (2023): 105163.

    5.  Ma, Linquan*, Jixin Wang, Han Chen, and Lan Liu†. "Semiparametrically Efficient Method for Enveloped Central Space." Journal of the American Statistical Association 119, no. 547 (2024): 2166-2177.

    6.  Cook, R. Dennis, Liliana Forzani, and Lan Liu†. "Envelopes for multivariate linear regression with linearly constrained coefficients." Scandinavian Journal of Statistics 51, no. 2 (2024): 429-446.

  • * indicates student

    † indicates corresponding author

    During collaboration with Dennis Cook, I got to know more of his research history. One thing struct me ...

    During collaboration with Dennis Cook, I got to know more of his research history. One thing struct me deeply: Dennis is known, among other things, his invention of "Cook's Distance". This method is taught even in undergraduate statistics courses. This method was developed when he worked with people from agriculture department on a very applied work. This prompted to me to get my hands dirty and digged into more applied research. I chose medical field because in this field, good research does save lives.

    Stroke-Cerebroprotection

    Normobaric Oxygen (OPENS)

    I designed a dose-escalation trial, whose results informed the dosage selection of the latter Phase IIb trial (OPENS-2).

    1.  W. Li, S. Wang, L. Liu, J. Chen, J. Lan, J. Ding, Z. Chen, S. Yuan, Z. Qi, M. Wei, X. Ji, (2024) Normobaric Hyperoxia Combined With Endovascular Treatment Based on Temporal Gradient: A Dose-Escalation Study”, Stroke.

    Thrombolysis

    1.  Y. Qiao, J. Wang, T. Nguyen, L. Liu,X. Ji, W. Zhao “Intravenous Thrombolysis with Urokinase for Acute Ischemic Stroke”, published in Brain Science 14:989.

    Antiplatelet

    1.  1.W. Zhao; S. Li; C. Li; C. Wu; J. Wang; L. Xing; Y. Wan; J. Qin; Y. Xu; R. Wang; C. Wen; A. Wang; L. Liu; J. Wang; H. Song; W. Feng; Q. Ma; X. Ji, (2024)“Safety and Efficacy of Intravenous Tirofiban for Early Neurological Deterioration Prevention in Patients with Acute Ischemic Stroke (TREND): A Multicentre, Prospective, Randomised, Open-Label, Blinded-endpoint Trial”, The Lancet Neurology.

    Cerebral venous thrombosis (RETIAN-CH)

    I designed the analysis plan for a.

    1.  H. Bian, X. Wang, L. Liu, F. Yan, S. Lu, W. Hui, C. Zhou, J. Duan, M. Li, J. Chen, R. Meng, L. Cao, L. Wang, X. Ji(2024) “Multicenter registry study of cerebral venous thrombosis in china (RETAIN-CH): Rationale and design” Brain and Behavior.

    2.  H. Bian, X. Wang, G. Liu, C. Zhou, R. Meng, L. Liu, J. Duan, F. Yan, C. Li, M. Li, W. Hui, X. Zhang, D. Zhao, Y. Li, Q. Fang, D. Kang, H. Zeng, Z. Liang, Z. Shi, W. Yue, Q. Sun, G. Chen, J. Song, Z. Yan, Q. Ji, K. Wang, L. Tong, X. Hu, W. Cao, W. Yan, R. Gao, Q. Li, J. Wang, Y. Liu, B. Wang, X. Wang, S. Yao, Y. Lang, H. Li, C. Anderson, X. Ji (2024+) “Endovascular treatment for cerebral venous thrombosis: a multicenter study in China (RETIAN-CH)” submitted.

Open positions and students

  • What does it Take?

    Doing good work in biostatistics is hard and requires a complex set of skills.

    Maths: You need maths to understand the statistical methods we use, and to come up with new methods. The least you should know is calculus and linear algebra.

    Statistics: You need to know probability, statistical inference as basis, and need to know the field of causal inference, model selection, and statistical learning.

    Biostatistics: This is distinct from statistics, as it brings in concrete contexts. These contexts might be arise from specific settings or regulatory requirements.

    Medicine: Domain knowledge is very important in applied statistical work. I remember during my PhD and post-doc years, my advisor could talk to doctors in their language while I thought they were talking in Greek. Some of the best biostatisticians/statisticians come from medical background. Don Rubin were a psychology student, Jamie Robins and Scott Emerson were previously doctors.

    Coding: This is required to carry out your ideas. R is required, and it will be a bonus if you know python, C++, or java. You need to write clean and efficient code. Of course, you need to be comfortable with your computers in general.

    Communication: Communication is under-rated during undergraduate work, but its importance could not be over-stated in a collaborative work. It involves not only the ability to understand others or get yourself understood, but also the gut to stand up for yourself and your principles when bullied or unfairly. For admission, you will be evaluated on the above six dimensions in addition to character. I do not expect everyone to be good at everything, but you need to be good in some dimensions. For example, I can understand if a medical students have not taken as many courses in maths and statistics. Conversely, I do not expect a statistcs student to be thoroughly trained in medicine. Admission exams favors maths and statistics, so medical students will a lower passing bar, but they need to be ready to pick up the maths once enrolled. I intend to create a group with diverse background, so that we can all learn from each other.

  • Master Program

    Written exam coverage: Calculus, Linear Algebra, Probability and Statistics, Biostatistics Oral exam coverage: all six dimensions listed.

  • PhD Program

    Written exam coverage: Calculus, Linear Algebra, Probability and Statistics, Biostatistics, Causal Inference.

    Oral exam coverage: all six dimensions listed.

    Important: If you do not come from medical background, please apply to the program under CIMR (创新中心).

  • How can I prepare for Admission exams

    Please refer to the Resources section on what book and classes to take. If you are coming from a non-standard background, I encourage you to take a half year (full time) to study for these. If finance is a problem, I offer a part-time lab assistant position--you will spend 6 hours a day assisting research, and the rest of the day learning the material. Pay is about 80k a year. I do NOT guarantee admission after this internship.

  • What do I look for in Application

    I look at the courses you take, the score you get (courses and CET-6), and a bit at the research you do. If you are a medical student, take some maths classes(高等数学,线性代数,概率论)and some statistics classes (try to take them from statistics department). If your school does not have that, take online courses, and let me know (or better show me proof of work, like the exercises you did) in application. Learn some coding and do some mini-projects with it (see Resources). Read some research in English. You can start with papers in NEJM, Lancet and JAMA series. Read them carefully, and try to figure out what questions they answered, how did they answer this. Pay particular attention to the methods used. No need to prepare a lengthy plan for PhD or Master. I do NOT look at this. You will need to learn a lot in a graduate program, and your plan will undoubtedly change.

Resources

To prepare for a successful career, you will need certain skills. I list some resources for part of the skill. Whether you choose to become my students or not, I think these resources will be helpful. If you are reading to study for admission exams, resources denoted with * are what admission exams will be based on, and ** are for PhD admission. Other resources share similar content, offer alternative explanations.