Off on a Tangent 18.08

Two colloquiums scheduled in the next fortnight

  • Title: The Numerical Range of the Product of a Composition Operator and an Adjoint of a Composition Operator
  • Speaker: Dr. Michael Dabkowski, University of Michigan-Dearborn
  • Time/Location: Thur, Feb 6 @ 4:00 PM in VWF 104

Abstract: Composition operators take a function and compose it with another function (called an inducing map) to form a new function. When we allow the functions considered to be complex-valued, we uncover a trove of mathematical connections. In this talk we will consider functions which are elements of the Hardy space and compose them with the monomials zk. When this composition operator is multiplied by an adjoint of a composition operator of the same form we see the structure of a weighted shift operator. We will define the numerical range of this operator, investigate its convexity, and show that by inputting collection of lacunary polynomials we can foliate the numerical range.

  • Title: Recidivism, Risk scores, and Race: An overview of potential biases and notions of fairness in statistical models for predicting recidivism in the U.S.
  • Speaker: Dr. Yew-Meng Koh, Hope College
  • Time/Location: Thur, Feb 13 @ 11:00 AM in the Fried-Hemenway Auditorium (MMC 135).

Abstract: Predicting recidivism with defendants’ recidivism risk scores has become increasingly widespread in the U.S., with these scores influencing consequential decisions in trials. Concern has been raised in some quarters about the equity of these predictions across racial groups and the estimation of the risk scores themselves. This talk focuses on various reasonable notions of statistical parity, how they relate to each other, and the impossibility of simultaneously satisfying all definitions of statistical parity. The trade-offs from adopting one notion of fairness over another are also discussed, and suggestions are made for a reasonable compromise between several competing definitions.

Statistics Showcase

The 18th annual Statistics Showcase, held Friday, January 17, recognized ten outstanding student statistics projects of the Fall 2019 semester. Congratulations go out to all of these students for their hard work and outstanding results. The following projects were presented.

  • “The Effect of Energy Drinks” by Scott Corman, Abigail Dieffenbach and Erica Hofman
  • “How Do You Retain Information Better?” by Nic Larson, Abby Rakus and Kylie Slavik
  • “Reaction Times” by Jo Cook, MeKenna VanKoevering and Paige Wilmer
  • “A Toy Story: Factors that Affect Children’s Toy Prices” by Yuki Kojima, Emily Smith and Yung Yue Tneh
  • “Comparing Analytical Methods: Intramurals and Grade Point Average” by Michael Boynton, Mason Fritz and Nicholas Hoffman
  • “Effects of Background Music on Short-Term Memorization Ability” by Lindsey Heidema, Grace Kennedy, Claire Leikert and Megan McCarthy
  • “The Jelly Bean Test” by Julia Hopkins, Terry Nguyen, Caiti Warne and Leyang Xu
  • “The Difference of Preference Between Coke and Pepsi” by Lindsey Badger and Kendall Bouma
  • “Gamers vs. Non-Gamers: Tests of Cognitive Skills” by TJ Abraham, Seth Piersma and Caleb Schoon
  • “Influence of Brand Name on Preference” by Elly Deneef
Participants in the 18th Annual Statistics Showcase

Joint Mathematics Meetings

Here are some more pictures from this year’s Joint Mathematics Meetings in Denver. Three Hope students, Cole Persch, Jack Krebsbach, and Eric Leu, are shown presenting their posters.

Also shown enjoying a lovely buffet at Mint India in Denver are Hope’s student presenters along with Dr. Yurk and Dr. Edwards, as well as former Hope students Nathan Graber, Jessalyn Bolkema, and David McMorris (and wife Marla Williams).


Have you seen any of these cool math buttons around? Do you have any? The mathematics department started making buttons this year and are giving them out to those that take mathematics classes; a different button for each class. Which classes do you think the buttons in the picture represent?

U of M Big Data Summer Institute

Are you interested in big data? The University of Michigan conducts an annual Big Data Summer Institute and it will be held June 15 to July 24 this coming summer. You can find more information on the flyer or on their website.

Hope students that have attended this program in the past have found it to be a great experience. We just received a note from the University of Michigan professor that runs the program and he said, “I am in the process of reviewing applications for the Big Data Summer Institute. Unfortunately there were no applications from Hope College, which is a bummer because we seemed to have great Hope students virtually every year at the Big Data Summer Institute. We make a particular effort to grab great in-state students.”

So if you are interested, check it out. They are waiting for your application.

Your Health Lecture Series

Michigan State University’s College of Human Medicine provides for an annual lecture series co-sponsored by Hope, MSU, and Holland Hospital. This year’s talk is titled, “Millions of Lives Saved: The Incredible Impact of Immunizations.” It will be presented by Dr. Keith English, a pediatric infectious disease specialist at Michigan State. The talk will be held at 7:00 PM on Tuesday, February 4 in Graves Auditorium.

Problem of the Fortnight

Sally leaves Scooteroplis on her scooter at the same time Billy leaves Bikeville on his motorozed bike.  They meet at a point 24 miles closer to Scooteropolis than to Bikeville.  At this point, they swapped vehicles and returned to their home towns.  Sally completed her trip 9 hours after the switch, and Billy returned to Bikeville 16 hours after the switch.  Assuming the scooter and motorized bike maintained constant (but different speeds), what is the distance between Scooteropolis and Bikeville.

Drop your solution in the Problem of the Fortnight slot outside Professor Mark Pearson’s office, room 212 in The Werf, by 3:00 p.m. on Friday, February 7.  As always, be sure to include your name and the name(s) of your math professor(s) — e.g. Phil N. deBlank, Professor S.A. Antser — on your solution.  Good luck and have fun!

Problem Solvers of the Fortnight

Congratulations to Camen Andrews, Colin Brown, Josh Brown, Sarah Brown, Anna Carlson, Liam Diephuis, Cameron Dunn, Ryan Miller, Matthew Nguyen, Cole Persch, Eleni Persinger, Forest Rulison, Shane Vaara, Bethany VanHouten, Kamaron Wilcox, Tom Yonker, and William Zywicki—all of whom correctly solved the problem in the last issue of America’s premiere fortnightly mathematics department news blog.

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