ivy's Picture

Ivy (I-Ming) Liu

BS, MS (Iowa State University), PhD (University of Florida),
Associate Professor
School of Mathematics and Statistics
Email: ivy.liu@vuw.ac.nz
Phone: +64 4 463 5648
ORCID: 0000-0002-3152-2632

Room: CO 356 Postal Address


Research Interests

My main area of interest is categorical data analysis, particularly

Multidisciplinary Research Impact

  • Education and Psychometrics: Differential Item Functioning (DIF)

    DIF analysis is commonly used in large-scale educational tests and survey studies. DIF analysis helps reveal whether the test or survey is fair, or whether it is systematically biased against certain groups of test-takers, such as women or certain underprivileged groups. The Liu-Agresti estimator (Liu and Agresti, 1996, DOI: 10.2307/2532838) is widely used when performance is scored according to the degrees of proficiency, rather then correct or incorrect. The Liu-Agresti method can be implemented by packages DIFAS 5.0, WINSTEPS (DIF statistics), etc.

  • Econometrics and Biomedical Science: Blow-Up and Cluster (BUC)

    The BUC method (Mukherjee, Ahn, Liu, Rathouz, and Sanchez, 2008, DOI: 10.1002/sim.3325) is named by Baetschmann et al. (2015). For a longitudinal study, researchers are often concerned about the unobserved heterogeneity. The BUC method provides a simple way to obtain consistent fixed effect estimators for an ordered logit model to control the unobserved heterogeneity. The BUC method was originally proposed for biomedical case-control data. Gunasekara, Carter, Liu, , Richardson, and Blakely (2012) first used the method for a longitudinal data.

  • Social Science: Multiple response data

    A multiple response variable is a categorical variable for which respondents can select any number of outcome categories. Such data arise often in a survey. For example, a question might be ``which of the following learning methods have you used'' and the respondents could tick all items that apply. We (DOI: 10.1111/j.0006-341X.1999.00936.x, DOI: 10.1177/0049124101029004001, DOI: 10.1002/bimj.200710395, DOI: 10.1111/insr.12015) used maximum-likelihood or quasi-likelihood approaches to analyse such data. Some of the methods can be implemented using packages SPSS, R (MRCV), etc.

    Research Projects, Funding and Scholarships

    Contact me if you want to do a PhD/MSc in my research areas and want to get a scholarship.

  • Research Assistantships:

    Research publications

    R Codes


    In 2022, I am teaching the following courses: