Bayesian tree based models and applications

We are looking for strong candidates to work on this exciting project described below!<br /> <br /> Bayesian classification and regression tree (BCART) and its ensemble version – Bayesian additive regression tree (BART) models – are powerful semiparametric learning techniques for modelling nonlinear regression functions that outperform many other machine learning methods. Classical BCART and BART models were proposed for continuous (Gaussian) and binary response variables (see, [1-3]), and over the years these have been extended to analyse a large class of response variables, including count data (see, [4]). Their excellent empirical performance has also motivated works on their theoretical foundations (see, [5]). <br /> <br /> One direction of research on this project is to try to understand the mechanism of the BCART and BART methods from a theoretical point of view. Another direction of research is to explore extended BCART and BART models with applications to areas such as insurance pricing (see [6]) or/and spatial-temporal data analysis (e.g., environmental or climate data modelling). Some key questions to be explored in these applications include feature selection, choice of loss functions, class-imbalance problem with zeros, model stability, and interpretability.<br /> <br /> References:<br /> <br /> [1] H. A. Chipman, E. I. George, and R. E. McCulloch, “Bayesian CART model search,” Journal of the American Statistical Association, vol. 93, no. 443, pp. 935–948, 1998.<br /> [2] D. G. Denison, B. K. Mallick, and A. F. Smith, “A Bayesian CART algorithm,” Biometrika, vol. 85, no. 2, pp. 363–377, 1998.<br /> [3] H. A. Chipman, E. I. George, R. E. McCulloch, et al., “BART: Bayesian additive regression trees,” The Annals of Applied Statistics, vol. 4, no. 1, pp. 266–298, 2010.<br /> [4] J. S. Murray, “Log-linear Bayesian additive regression trees for multinomial logistic and count regression models,” Journal of the American Statistical Association, vol. 116, no. 534, pp. 756–769, 2021.<br /> [5] V. Rockova, S. Van der Pas, et al., “Posterior concentration for Bayesian regression trees and forests,” Annals of Statistics, vol. 48, no. 4, pp. 2108–2131, 2020.<br /> [6] Y. Zhang, L. Ji, Aivaliotis, and C.C. Taylor, ‘’Bayesian CART models for insurance claims frequency”. 2023. Available at https://arxiv.org/pdf/2303.01923.pdf<br />

<p>Formal applications for research degree study should be made online through the <a href="https://www.leeds.ac.uk/research-applying/doc/applying-research-degrees">University's website</a>. Please state clearly in the Planned Course of Study Section that you are applying for <em><strong>PHD Statistics FT,</strong></em> in the research information section that the research degree you wish to be considered for is <em><strong>Bayesian tree based models and applications</strong></em><span style="font-size:11pt"><span style="line-height:107%"><span style="font-family:Calibri,sans-serif"><span style="font-family:"Arial",sans-serif"> </span></span></span></span>as well as <a href="https://eps.leeds.ac.uk/maths/staff/5350/dr-lanpeng-ji">Dr Lanpeng Ji</a> as your proposed supervisor and in the finance section, please state clearly <em><strong>the funding that you are applying for, if you are self-funding or externally sponsored</strong></em>.</p> <p>If English is not your first language, you must provide evidence that you meet the University's minimum English language requirements (below).</p> <p><em>As an international research-intensive university, we welcome students from all walks of life and from across the world. We foster an inclusive environment where all can flourish and prosper, and we are proud of our strong commitment to student education. Across all Faculties we are dedicated to diversifying our community and we welcome the unique contributions that individuals can bring, and particularly encourage applications from, but not limited to Black, Asian, people who belong to a minority ethnic community, people who identify as LGBT+ and people with disabilities. Applicants will always be selected based on merit and ability.</em></p> <p class="MsoNoSpacing">Applications will be considered after the closing date.  Potential applicants are strongly encouraged to contact the supervisors for an informal discussion before making a formal application.  We also advise that you apply at the earliest opportunity as the application and selection process may close early, should we receive a sufficient number of applications or that a suitable candidate is appointed.</p> <p class="MsoNoSpacing"><strong>Please note that you must provide the following documents in support of your application by the closing date of Monday 3 March 2025 if applying for Leeds Doctoral Scholarship or Tuesday 1 April 2025 for Leeds Opportunity Research Scholarship.</strong></p> <p><strong>If you are applying for the School of Mathematics Scholarship 2025/26, or with external sponsorship or you are funding your own study, please ensure you provide your supporting documents at the point you submit your application:</strong></p> <ul> <li>Full Transcripts of all degree study or if in final year of study, full transcripts to date</li> <li>Personal Statement outlining your interest in the project</li> <li>CV</li> </ul>

Applicants to research degree programmes should normally have at least a first class or an upper second class British Bachelors Honours degree (or equivalent) in an appropriate discipline. The criteria for entry for some research degrees may be higher, for example, several faculties, also require a Masters degree. Applicants are advised to check with the relevant School prior to making an application. Applicants who are uncertain about the requirements for a particular research degree are advised to contact the School or Graduate School prior to making an application.

The minimum English language entry requirement for research postgraduate research study is an IELTS of 6.0 overall with at least 5.5 in each component (reading, writing, listening and speaking) or equivalent. The test must be dated within two years of the start date of the course in order to be valid. Some schools and faculties have a higher requirement.

<p style="margin-bottom:12px"><strong>Self-Funded or externally sponsored students are welcome to apply.</strong></p> <p><strong>UK</strong> – The <a href="https://phd.leeds.ac.uk/funding/138-leeds-doctoral-scholarship-2025-faculty-of-engineering-and-physical-sciences#:~:text=Key%20facts&text=One%20Leeds%20Doctoral%20Scholarship%20is,rata%20for%20part%2Dtime%20study.">Leeds Doctoral Scholarship</a> <strong>(closing date: Monday 3 March 2025)</strong>, <a href="https://phd.leeds.ac.uk/funding/234-leeds-opportunity-research-scholarship-2022">Leeds Opportunity Research Scholarship</a> <strong>(closing date: Tuesday 1 April 2025)</strong> and <a href="https://phd.leeds.ac.uk/funding/55-school-of-mathematics-scholarship-2025-26">School of Mathematics Scholarship 2025/26</a> <strong>(open from October 2024)</strong> are available to UK applicants.</p> <p><strong>Non-UK</strong> – <a href="https://phd.leeds.ac.uk/funding/55-school-of-mathematics-scholarship-2025-26">School of Mathematics Scholarship 2025/26</a> <strong>(open from October 2024)</strong> are available to all International applicants.  The <a href="https://phd.leeds.ac.uk/funding/48-china-scholarship-council-university-of-leeds-scholarships-2021">China Scholarship Council - University of Leeds Scholarship</a> <strong>(now closed for October 2025 entry)</strong> is available to nationals of China. The <a href="https://phd.leeds.ac.uk/funding/73-leeds-marshall-scholarship">Leeds Marshall Scholarship</a> is available to support US citizens. <a href="https://phd.leeds.ac.uk/funding/60-alumni-bursary">Alumni Bursary</a> is available to graduates of the University of Leeds.</p> <p>You will be responsible for paying the overtime fee in full in your writing up/overtime year (£320 in Session 2024/25), but the scholarship maintenance allowance will continue to be paid for up to 6 months in the final year of award.</p> <p><strong>Important: </strong>Please note that that the award does <em><strong>not</strong></em> cover the costs associated with moving to the UK.  All such costs (<a href="https://www.leeds.ac.uk/international-visas-immigration/doc/applying-student-visa">visa, Immigration Health Surcharge</a>, flights etc) would have to be met by yourself, or you will need to find an alternative funding source. </p> <p>Please refer to the <a href="https://www.ukcisa.org.uk/">UKCISA</a> website for information regarding Fee Status for Non-UK Nationals.</p>

<p>For general enquiries about applications, please contact PGR Admissions by email to <a href="mailto:maps.pgr.admissions@leeds.ac.uk">maps.pgr.admissions@leeds.ac.uk</a>. </p> <p>For questions about this research project, please contact Dr Lanpeng Ji by email to <a href="mailto:l.ji@leeds.ac.uk">l.ji@leeds.ac.uk</a></p>