Julie Horrocks

Professor, Statistics
Phone number: 
519-824-4120 x56556 or 53291
MacNaughton 437 or 518

Part of my research is in developing and applying statistical models for data that arise in medical research.  These data usually involve an element of time, so are either longitudinal or time to event data. I also work with joint models that quantify the effect of longitudinal data on the time to some event. Missing values are usually present and special techniques are required.

Another branch of my research is statistical models that account for spatial correlation. These models are used in spatial epidemiology and the estimation of animal abundance.

A Masters degree in Statistics can lead to an immediate job or future study. Former students of mine have obtained employment as data analysts at various businesses and institutions, including

  • Bell Business Intelligence
  • Statistics Canada
  • Monsanto
  • Athena Software, Waterloo
  • Sick Kids Hospital in Toronto
  • Robarts Clinical Trials
  • Population Health Research Institute,Hamilton
  • Vividata, Toronto
  • Bridgeport Health
  • Canadian Automobile Association (CAA) 
  • Scotiabank
  • Cetero Research
  • Economical Insurance
  • ING Direct
  • Quantics, Scotland

Professional Statistician (P.Stat) designation, obtained June 3, 2012.  This is a program of accreditation, offered by the Statistical Society of Canada.  The qualification of P.Stat indicates that the holder has the equivalent of an honours degree in statistics, a minimum of six years of professional experience in the application of statistics, and is bound by a Code of Ethics.

  • PhD
    • Joint Models for Overall and Progression-Free Survival (in progress)
    • Variable Selection for Spatial Point Process Models (in progress).
    • Survival Analysis with Internal Categorical Time-varying Covariates (2017).
    • Ties Between Event Times and Covariate Change Times in Cox Models (2014).
  • MSc
    • Random and Rotation Forests (in progress)
    • Tree-based methods for longitudinal data (in progress)
    • Regression Splines For Longitudinal Data (2016).
    • An evaluation of abundance estimators for sea lamprey using stratified mark recapture data (2015).
    • Ordinal Logistic Regression With Survey Weights (2016).
    • The Effect of Diagnostic Misclassification on Spatial Statistics for Regional Data (2014).
    • Regression Methods for Left-censored Data (2014).
    • Internal covariates in survival analysis (2013).
    • A Comparison of Frailty Regression Models (2012).
    • Methods for Missing Zero-Inflated Data (2012).
    • Statistical Models for Zero-Inflated Longitudinal Data (2011).
    • A Study Of Ties And Time-Varying Covariates In Survival Analysis (2011).
    • Quantifying Family History for Mental Illness (2011).
  • Undergraduate 4th year Independent Research Projects
    • Effect of Dropout on Statistical Models for Bipolar Disorder
    • Spatial Analysis of Gonorrhea in Southern Ontario (2016).
    • Network Sampling (2015).
    • Bayesian Models for Lake Huron Whitefish Catch Data with Excess Zeros (2015).
    • Estimating Abundance of Seabirds (2014).
    • Methods for Right-Truncated Data (2013).
    • Bayesian Approaches to Estimating Marine Abundance (2012).

B.Sc. (Mount Allison University), 1980.
B.F.A. (Nova Scotia College of Art & Design), 1986.
M.Math. (University of Waterloo), 1993.
Ph.D. (University of Waterloo), 1999.

  • A Duffy, C Keown-Stoneman, S Goodday, J Horrocks, A Weir, P Grof, K Saunders and J Geddes. Daily and weekly mood symptom ratings using remote capture methods in high-risk offspring of bipolar parents. Lancet Psychiatry. Submitted.
  • J Daniel, J Horrocks, G Umphrey (2018). Penalized composite likelihoods for inhomogeneous Gibbs point process models. Computational Statistics and Data Analysis. 24: 104-116.
  • C Keown-Stoneman, J Horrocks, G Darlington (2018). Exponential decay for binary time-varying covariates in Cox models. Statistics in Medicine. 37(5), 776-788.
  • C Keown-Stoneman, J Horrocks, G Darlington (2017). Weibull multi-state models with misclassification. Communications in Statistics – Simulation and Computation. DOI: 10.1080/03610918.2017.1371751
  • S Goodday, J Horrocks, C Keown-Stoneman, P Grof, A Duffy (2016). Repeated salivary daytime cortisol and onset of mood episodes in offspring of bipolar parents. International Journal of Bipolar Disorder. 4:12.
  • C Keown-Stoneman, J Horrocks, G Darlington, S Doucette, A Duffy (2015). Multi-state models for investigating possible stages leading to bipolar disorder. International Journal of Bipolar Disorder. Feb 24, 2015. 3:5. DOI 10.1186/s40345-014-0019-4
  • X Xin, J Horrocks, G Darlington (2018). Weighting Methods for Ties Between Event Times and Covariate Change Times, Communications in Statistics - Simulation and Computation. Published online 25 Mar 2015. 47:1 1-15.
  • J Horrocks, M Rueffer, D Gillis, S Wong, D Hamilton (2015). Estimation of Abundance from a Correlated Binary Time Series. In Cojocaru, M., Kotsireas, I.S., Makarov, R.N., Melnik, R., Shodiev, H. (Eds.), Interdisciplinary Topics in Applied Mathematics, Modeling and Computational Science Series: Springer Proceedings in Mathematics & Statistics, Vol. 117. DOI: 10.1007/978-3-319-12307-3_34.
  • Duffy A, Horrocks J, Doucette S, Keown-Stoneman C, McCloskey S, Grof P (2014). The developmental trajectory of bipolar disorder. British Journal of Psychiatry. 204: 122–28.
  • M Rueffer, J Horrocks (2014). A Bayesian Approach to Estimating Animal Density from Binary Acoustic Transects. Computational Statistics and Data Analysis, 80(C), 17-25.
  • Duffy A, Horrocks J, Doucette S, Keown-Stoneman C, McCloskey S, Grof P (2013). Childhood anxiety: An early predictor of mood disorders in offspring of bipolar parents. Journal of Affective Disorders 150 (2), 363-369.
  • X Xin, J Horrocks, GA Darlington. (2013). Ties between event times and jump times in the Cox model. Statistics in Medicine. 32(14) 2374-2389.
  • KA Martin Ginis, KP Arbour-Nicitopoulos, AE Latimer-Cheung, AC Buchholz, SR Bray, BC Craven, KC Hayes, MA McColl, PJ Potter, K Smith, D L Wolfe, R Goy, J Horrocks (2012). Predictors of Leisure Time Physical Activity Among People with Spinal Cord Injury. Annals of Behavioral Medicine. 44(1):104-118. doi 10.1007/s12160-012-9370-9.
  • A Duffy, J Horrocks, R Milin, S Doucette, G Persson, P Grof (2012). Adolescent substance use disorders during the early stages of bipolar disorder: A prospective high-risk study. Journal of Affective Disorders.142(1-3): 57-64. doi:10.1016/j.jad.2012.04.010
  • J Horrocks, D Hamilton, H Whitehead. (2011). A Likelihood Approach to Estimating Abundance from Binary Acoustic Transects. Biometrics. 67(3): 681-690. doi: 10.1111/j.1541-0420.2010.01496.