Spring 2025 PSQF 6270 Section 0001: Generalized Linear Models

Planned Schedule of Events (Printable Syllabus last updated 1/21/25)

Schedule of Topics and Events:

This course will meet synchronously in person and on zoom. The planned schedule of topics and events may need to be adjusted throughout the course. The online syllabus above will always have the most current schedule and corresponding due dates (i.e., the printable syllabus will not be updated unless noted).

Course Objectives, Prerequisites, and Materials:

This course will illustrate the uses of generalized linear models for predicting univariate and multivariate outcomes. The course objective is for participants to be able to complete all the necessary steps in a generalized linear model analysis: deciding which type of model is appropriate, creating predictor variables, building models to evaluate unique effects of predictors, and interpreting and presenting empirical findings. Prior to enrolling, participants should be comfortable with general linear models (e.g., regression, ANOVA), such as is covered in PSQF 6243.

Class time will be devoted primarily to lectures, examples, and spontaneous review, the materials for which will be available for download above. Readings and other resources have been suggested for each topic and may be updated later. Synchronous attendance (in person or via zoom) is strongly encouraged but is not required, and you do not need to notify the instructor of sporadic class absence. Video recordings of each class will be available on YouTube so that closed captioning will be provided, and supplemental videos may be added as well. Auditors and visitors are always welcome to attend class. No required class sessions will be held outside the regular class time noted above (i.e., no midterm or final exam sessions). However, because the course will have an applied focus requiring statistical software, participants are encouraged to attend group-based zoom office hours, in which multiple participants can receive immediate assistance near-simultaneously.

Course Requirements:

Participants will have the opportunity to earn up to 100 total points by completing work outside of class:

• Up to 72 points can be earned from homework assignments (HW; 5 planned initially) through a custom online system or ICON as noted—these will be graded for accuracy. HW that involves individual writing will have the opportunity to be revised once to earn the maximum points. Written assignments must be at least ¾ complete to be accepted. Unless otherwise instructed, please use “track changes” and retain all original instructor comments so that the instructor can see how your revisions address the comments.
• Up to 8 points may be earned from submitting formative assessments (FA; 4 planned initially) through ICON. For each, participants will receive 2 points for effort only—incorrect answers will not be penalized.
• Up to 20 points can be earned from “bridge” assignments (Bridge; 4 planned initially) through ICON. For each, participants will receive 3 points for effort only, and up to another 2 points based on degree of accuracy.
• Participants may earn up to 2 extra credit points for completing HW0; there may be other opportunities to earn extra credit at the instructor's discretion.

Revisions to the planned course schedule and/or content may result in fewer activities (and thus fewer total points) at the instructor's discretion. If that happens, this syllabus will be updated to reflect the new point totals.

Policy on Accepting Late Work and Grades of Incomplete:

Participants may submit work anytime during the semester to be counted towards their grade. However, to encourage participants to keep up with the class, late work will incur the following penalties (overall, not per day):

• Late HW will incur a 2-point penalty.
• Late HW plans, HW written revisions, or FAs will incur a 1-point penalty.
• Late bridge assignments will receive a maximum of 3 points (i.e., no points for accuracy then will be possible, given that correct answers will be discussed during the next class session ).
• Extensions will be granted for extenuating circumstances (e.g., conferences, comprehensive exams, family obligations) if requested at least two weeks in advance of the due date.

A final grade of "incomplete" will only be given in dire circumstances and entirely at the instructor's discretion. All work must be submitted by Thursday, May 15, 2025 at 11:59 PM to be included in the course grade.

Final grades will be determined according to the percentage earned of the total possible points:

>96% = A+, 93–96% = A, 90–92% = A−, 87–89% = B+, 83–86% = B, 80–82% = B−, 77–79% = C+, 73–76% = C, 70–72% = C− (PASS), 67–69% = D+, 63–66% = D, 60–62% = D−, <60% = F

Course Software:

Participants will need to have access to statistical software—STATA, or R+RStudio—that can estimate the models presented. Each of these programs is freely available to course participants in multiple ways:

• You can connect to the U Iowa Virtual Desktop (connect to the U Iowa VPN first) for free
• You can connect to the U Iowa Research Remote Desktop (connect to the U Iowa VPN first) for free
• You can install R software for free on your local machine, along with the free graphical RStudio interface that makes R easier to use (install second after R software)
• You could also pay $48 to install a 6-month student copy of STATA on your local machine

SAS may also be used for specific examples throughout the course. The last unit of the course on path analysis will also use Mplus software. Both of these are freely available on the U Iowa Virtual Desktop.

Academic Misconduct:

As a reminder, the University of Iowa College of Education has a formal policy on academic misconduct, which all students in this course are expected to follow. While students can work with each other to understand the course content, all course activities must be completed individually. Please consult the instructor if you have questions.

The use of ChatGPT or any other Artificial Intelligence (AI) should not be needed (or helpful) , as the course materials will provide examples of all software code needed to complete HW. Similarly, the use of AI in completing FAs or bridge activities will defeat their purpose, as these structured reviews are designed to help participants recognize remaining sources of confusion or inexperience (and 2 points for each will be given for each regardless, so long as there is some effort made in trying to answer each question). In any written homework, the uncredited use of AI will be treated as academic misconduct. Acceptable uses of AI are limited to grammatical and proof-reading advice (and should be credited).

Respect for Each Other:

The instructor wants ALL students to feel welcome and encouraged to participate in this course. There is no such thing as a “stupid” question (or answer). All course participants—enrolled students and auditing visitors—should always feel welcome to ask whatever questions will be helpful in helping them understand the course content. Questions or comments are welcome at any point during class (aloud or using the zoom chat window), in office hours, over email, or in individual appointments with the instructor (available by request). Students with disabilities or who have any special circumstances are encouraged to contact the instructor for a confidential discussion of their individual needs for academic accommodation.

All participants are welcome to attend class via zoom instead of in person for any reason at any time. If it possible that you have been exposed to COVID-19 or any other illness, please DO NOT attend class in person! Similarly, if the instructor has been exposed to illness or the weather prohibits safe travel to class, the course will move to a temporary zoom-only format to protect all course participants.

When using zoom, please provide the name you wish for us to call you inside your zoom account (i.e., so that it appears on your window while in use). Student use of cameras and microphones while on zoom is also encouraged but not required (out of respect for your privacy and/or limited internet). Please note that class video recordings posted to YouTube will NOT include any video from course participants (only the class audio and screen share from the instructor will be captured). Participants who do not wish for their audio to be captured can use the zoom chat window (which also allows for private direct messages to the instructor), even while attending in person.

The University of Iowa is committed to making the class environment (in person or online) a respectful and inclusive space for people of all gender, sexual, racial, religious, and other identities. Toward this goal, students are invited to optionally share the names and pronouns they would like their instructors and advisors to use to address them. The University of Iowa prohibits discrimination and harassment against individuals on the basis of race, class, gender, sexual orientation, national origin, and other identity categories. For more information, contact the Office of Civil Rights Compliance. Additional university guidelines about classroom behavior and other student resources are provided here, student complaint procedures are provided here, and the university acknowledgement of land and sovereignty is provided here.

Respect for The Rest of Your World:

The instructor realizes that this course is not your only obligation in your work or your life. While class attendance in real time is not mandatory, it is strongly encouraged because frequent review of the material will be your best strategy for success in this course. However, if work or life events may compromise your ability to succeed, please contact the instructor for a confidential discussion so that we can work together to make a plan for your success. Please do not wait until you are too far behind to try to catch up!

Course Textbook:

(H & H): Hardin, J. W. & Hilbe, J. M. (2018). Generalized linear models and extensions (4th ed.). STATA Press. Available from the U of Iowa library as an e-book (for one user at a time).

Recommended Textbook for Background on General Linear Models (as needed for review):

Darlington, R. B., & Hayes, A. F. (2016). Regression analysis and linear models: Concepts, applications, and implementation. Guilford. Available from the U Iowa library as an e-book (for multiple users at the same time).

Other Course Readings (all available in ICON under "Files"):

Note—I know this is A LOT of readings, but we are covering a lot of material! I have included these sources to give you some additional tutorials and examples. I encourage you to read as many of these sources as possible, but your priority should be to participate in class and complete course work first!

Agresti, A. (2015). Foundations of linear and generalized linear models. Wiley & Sons.

Bürkner, P.-C., & Vuorre, M. (2019). Ordinal regression models in psychology: A tutorial. Advances in Methods and Practices in Psychological Science, 2(1), 77–101. https://doi.org/10.1177/2515245918823199

Certo, S. T., Busenbark, J. R., Kalm, M., & LePine, J. A. (2020). Divided we fall: How ratios undermine research in strategic management. Organizational Research Methods, 23(2), 211–237. https://doi.org/10.1177/1094428118773455

Enders, C. K. (2010; chapters 3–5). Applied missing data analysis. Guilford.

Finsaas, M. G., & Goldstein, B. L. (2021). Do simple slopes follow-up tests lead us astray? Advancements in the visualization and reporting of interactions. Psychological Methods, 26(1), 38–60. https://psycnet.apa.org/doi/10.1037/met0000266

Gonzales, O., Valente, M. J., Cheong, J., & MacKinnon, D. P. (2023). Mediation/indirect effects in structural equation modeling. In R. H. Hoyle (Ed.) Handbook of structural equation modeling (2nd ed.), pp. 409–426. Guilford.

Green, J. A. (2021). Too many zeros and/or highly skewed? A tutorial on modelling health behaviour as count data with Poisson and negative binomial regression. Health Psychology and Behavioral Medicine, 9(1), 436-455. https://doi.org/10.1080/21642850.2021.1920416

Hardin, J. W., & Hilbe, J. M. (2014). Estimation and testing of binomial and beta-binomial regression models with and without zero inflation. The Stata Journal, 14(2), 292–303. https://journals.sagepub.com/doi/pdf/10.1177/1536867X1401400204

Hoffman, L. (2015 chapters 2–3). Longitudinal analysis: Modeling within-person fluctuation and change. Routledge / Taylor & Francis. Also available at the University of Iowa library in electronic form.

Hsieh, F. Y. (1989). Sample size tables for logistic regression. Statistics in Medicine, 8(7), 795–802. https://doi.org/10.1002/sim.4780080704

Johfre, S. S., & Freese, J. (2021). Reconsidering the reference category. Sociological Methodology, 51(2), 235–269. https://doi.org/10.1177/0081175020982632 (see also the active link here)

Knief, U., & Forstmeier, W. (2021). Violating the normality assumption may be the lesser of two evils. Behavior Research Methods, 53, 2576–2590. https://doi.org/10.3758/s13428-021-01587-5

Konstantopoulos, S., Li, W., Miller, S., & van der Ploeg, A. (2019). Using quantile regression to estimate intervention effects beyond the mean. Educational and Psychological Measurement, 79(5), 883–910. https://doi.org/10.1177/0013164419837321

Kumle L., Võ, M. L.-H., & Draschkow, D. (2021). Estimating power in (generalized) linear mixed models: An open introduction and tutorial in R. Behavior Research Methods, 53, 2528–2573. https://doi.org/10.3758/s13428-021-01546-0

Long, J. S. (1997 chapter 7). Regression models for categorical and limited dependent variables. Sage.

McCabe, C. J., Halvorson, M. A., King, K.M., Cao, X., & Kim, D. S. (2022). Interpreting interaction effects in generalized linear models of nonlinear probabilities and counts. Multivariate Behavioral Research, 57(2–3), 243-263. https://doi.org/10.1080/00273171.2020.1868966

McGinley, J. S., Curran, P. J., & Hedeker, D. (2015). A novel modeling framework for ordinal data defined by collapsed counts. Statistics in Medicine, 34(15), 2312–2324. https://doi.org/10.1002/sim.6495

Mize, T. (2019). Best practices for estimating, interpreting, and presenting nonlinear interaction effects. Sociological Science 6(4), 81–117. http://dx.doi.org/10.15195/v6.a4

Rohrer, J. M., & Arslan, R. C. (2021). Precise answers to vague questions: Issues with interactions. Advances in Methods and Practices in Psychological Science, 4(2), 1–19. https://doi.org/10.1177/25152459211007368

Williams, R. (2016). Understanding and interpreting generalized ordered logit models. The Journal of Mathematical Sociology, 40(1), 7–20. https://doi.org/10.1080/0022250X.2015.1112384