Home Page for Henrik Stryhn

Henrik Stryhn

Welcome to my home page.

I am a statistician, coming from Denmark. From September 1st 2001, I work as associate professor in biostatistics at the Atlantic Veterinary College, University of Prince Edward Island, PEI, Canada. My Danish homepage, as of 27/9-2001, summarizes my work in research and teaching up till my move to Canada.

My current work involves research, teaching, supervision and consulting in statistical methods for veterinary epidemiology. I'm a member of, and contributor to, the Centre for Veterinary Epidemiological Research (CVER).

Some upcoming and recent activities

ISVEE XIII (August 2012, Maastricht, Netherlands), possibly offering a pre-conference course on multilevel modelling (with Ian Dohoo),
Epi on the Island summer course: Introduction to Multi-level Modelling, joint with Ian Dohoo, Prince Edward Island, July 10-14, 2011,
Annual meeting of the Statistical Society of Canada, June 2011, Wolfville; Estimating correlated frailties in a Cox model (abstract, text file).
Workshop on Survival Analysis, May 2011, Copenhagen.
Atlantic conference on Statistical Modelling of Environmental and Health Data, Fredericton, New Brunswick, August 18-20, 2010 (presentation).
Visits to Canadian veterinary colleges, June 7-11, 2010 (Calgary/Saskatoon/Guelph presentation; St-Hyacinthe presentation) (zipped Powerpoint).
Annual meeting of the Statistical Society of Canada, May 2010, Quebec City; A hierarchical latent class model for comparing individual and composite tests (abstract, text file).
Workshop on Advanced Multilevel Modelling with Emphasis on Discrete Outcomes, April 2010, Copenhagen.
ISVEE XII (August 2009, Durban, South Africa):
1. Pre-conference course "Introduction to Survival analysis" (with Ian Dohoo),
2. Contributed paper "Statistical methods for "messy" binary repeated measures data" (with Elmabrok Masaoud; link to PowerPoint presentation)
Course: Introduction to Multi-level Modelling, joint with Ian Dohoo, Prince Edward Island, June 15-19, 2009,
7th International Amsterdam Conference on Multilevel Analysis (April 2009, Amsterdam, Netherlands),
Course: Meta-analysis, assisting teacher for course by Javier Sanchez and Ian Dohoo, in connection with the CAVEPM conference 2008. May 21-30, 2008, Prince Edward Island,
Course: Introduction to multi-level modelling, joint with Ian Dohoo, May 6-9, 2008, Ghent, Belgium,
Summer courses on Multilevel Analysis, and Bayesian analysis and MCMC methods, joint with William Browne, Ian Dohoo and Javier Sanchez, Prince Edward Island, August 15-24, 2007,
ISVEE XI (August 2006, Cairns, Australia):
1. Contributed paper "Interpretation of Variance Parameters in Multilevel Poisson Regression Models" (with Javier Sanchez, Paul Morley, Calvin Booker, Ian Dohoo; Powerpoint presentation)
2. Contributed paper "Contextual Multilevel Models: Effects and Correlations at Multiple Levels" (with Sarne De Vliegher, Herman Barkema; Powerpoint presentation)
Likelihood-based inference for hierarchical/mixed statistical models, August 7-18, 2005, Tune, Denmark; course organized by the Dina Research School,
Annual meeting of the Statistical Society of Canada, May-June 2004, Montreal, A hierarchical latent class model for comparing individual and composite tests (presentation overheads, pdf-file).

Research

One particular interest of mine has been statistical models for observational data, typically extracted from registers of routinely recordings in animal production. The statistical methods relevant to such data include survival analysis and linear or generalised linear mixed models. Some references to my work in these fields:

Veterinary Epidemiologic Research, 2nd edition (2009 textbook by Dohoo, Martin and Stryhn)
Joint work with a graduate student, Elmabrok Masaoud on statistical models for binary repeated measures data,
The effect of season on somatic cell count and the incidence of clinical mastitis (Journal of Dairy Science 90, 1704-15; joint work with Richard Olde Riekerink and Herman Barkema)
Intra-unit correlations in seroconversion to Actinobacillus pleuropneumoniae and Mycoplasma hyopneumoniae at different levels in Danish multi-site pig production facilities (Preventive Veterinary Medicine 63, 9-28; joint work with Håkan Vigre, Ian Dohoo and Erika Busch),
The use of multilevel models to evaluate sources of variation in reproductive performance in dairy cattle in Reunion Island (Preventive Veterinary Medicine 50, 127-44; joint work with Ian Dohoo and Emmanuel Tillard).
Simulation as a tool of validation in hierarchical generalised linear models (presentation at ISVEE IX, August 2000, Colorado; joint work with Ian Dohoo, Emmanuel Tillard and Tine Hagedorn-Olsen).

Other topics of my (present or previous) interest are

Statistical modelling in veterinary epidemiology,
- Confidence intervals by the profile likelihood method, with applications in veterinary epidemiology (Stryhn, Christensen);
  contributed paper at ISVEE X (November 2003, Chile): abstract, Powerpoint presentation (zipped), SAS program for example 1, SAS program for example 2, SAS program for estimation of ICC in a beta-binomial distribution,
- Estimating transfer of bovine virus-diarrhoea virus in Danish cattle by use of register data (Prev Vet Med 52, 133-146; joint work with Lis Alban et al.).
- Risk factors for infection of sow herds with porcine reproductive and respiratory syndrome (PRRS) virus (Prev Vet Med 53, 83-101; joint work with Sten Mortensen et al.).
Meta analysis, in particular random involving effects models,
- Evaluation of underlying risk as a source of heterogeneity in meta-analyses: A simulation study of Bayesian and frequentist implementations of three models (Prev Vet Med 81, 38-55; joint work with Ian Dohoo and Javier Sanchez).
Risk analysis, in particular quantitative risk assessment,
Scenario tree models for quantifying freedom of disease,
Diagnostic testing, in particular latent class models,
- Using pseudogold standards and latent-class analysis in combination to evaluate the accuracy of three diagnostic tests (Prev Vet Med 85, 207-225; joint work with Pascale Nerette et al.).
- Thermophilic Campylobacter spp. in turkey samples: evaluation of two automated enzyme immunoassays and conventional microbiological techniques (Journal of Applied Microbiology 92, 574-82; joint work with Birgitte Borck, Annette Ersbøll and Karl Petersen).
Biological sequence analysis,
Spatial statistics,
Image analysis, in particular change-point models for image segmentation - the topic of my PhD thesis,
as well as many aspects of classical statistics.

For (a subset of) published papers, carry out a PubMed search. Earlier papers may be found at my previous Danish homepage.

Teaching

In the fall semester of 2011, I'll teach the introductory biostatistics course VHM 801. In the winter semester of 2012, I will teach the advanced biostatistics course VHM 802.

In the fall semesters of 2007-2009, I also taught a small component of the Epidemiology 1 (VHM 811) course on confounding and interaction. In the fall semester of 2009 I taught the special ("directed studies") course Statistical analysis of generalized, linear and mixed models . In the winter semester of 2005, I gave a special ("directed studies") course Statistical analysis of repeated measures models .

Other teaching material

Longitudinal data: simple univariate methods of analysis (15 pp., March 1998)

Supervision

At the Atlantic Veterinary College, I'm currently serving on graduate committees of the following graduate students:

Signe Andersen
Annie Wagener
Jennifer McCarron
Denise Methe
Carrie Lavers
Jackie Ellis

and I am supervising the following graduate students:

Nicole O'Brien (PhD, from Fall 2004, joint supervision with Dr. Larry Hammell)
Shanna Farrell (MSc, from Spring 2007, joint supervision with Dr. Kim Critchley)
Adel Elghafghuf (PhD, from Fall 2009)

For more information about the students, visit the students webpage at the Centre for Veterinary Epidemiological Research.
Supervised students at AVC/UPEI that have completed their programs include

Dan Kunic (Master of Applied Health Sciences Research, 2008)
Elmabrok Masaoud (PhD in Epidemiology/Biostatistics, 2009)
Tim Burnley (PhD in Epidemiology, 2011; joint supervision with Dr. Larry Hammell)

Consulting

As part of my commitment to servicing the entire Atlantic Veterinary College consultancies are provided on applied statistical problems (design or analysis) towards students and staff/faculty at the college. Consultations can be booked by the secretaries of the Department of Health Management, usually of half an hour or one hour's length.

Administration/Organisation

From the academic year 2009-2010, member of the UPEI Senate.
From 2001, member of the Graduate Studies and Research Committee at the Atlantic Veterinary College.
From 2008, webmaster for the webiste of Centre for Veterinary Epidemiological Research (CVER).
During the years 1999-2003, member of the board and webmaster for the Danish Society for Theoretical Statistics.

Address

Department of Health Management, Atlantic Veterinary College, University of P.E.I., Charlottetown, Prince Edward Island, C1A 4P3 CANADA, phone: (1-902) 894-2847, fax: (1-902) 566-0823, e-mail: hstryhn@upei.ca.

Henrik Stryhn (hstryhn@upei.ca) 2011-10-31