Mathematical Modeling in the Social and Life Sciences Michael Olinick Middlebury College DEDICATION To Judy who, without resort to mathematics, is a model wife, parent, and citizen Publisher: LaurieRosatone AcquisitionsEditor: DavidDietz ContentEditor: JacquelineSinacori EditorialAssistant: MichaelO’Neal ProductDesigner: TomKulesa CoverDesigner: KenjiNgieng MarketingManager: MelanieKurkjian AssociateProductionManager: JoycePoh SeniorProductionEditor: JoleneLing ThisbookwassetbyMPSLimited. Foundedin1807,JohnWiley&Sons,Inc.hasbeenavaluedsourceofknowledgeandunderstandingformore than200years,helpingpeoplearoundtheworldmeettheirneedsandfulfilltheiraspirations.Ourcompanyisbuilt onafoundationofprinciplesthatincluderesponsibilitytothecommunitiesweserveandwhereweliveandwork. 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Evaluationcopiesareprovidedtoqualifiedacademicsandprofessionalsforreviewpurposesonly,foruseintheir coursesduringthenextacademicyear.Thesecopiesarelicensedandmaynotbesoldortransferredtoathird party.Uponcompletionofthereviewperiod,pleasereturntheevaluationcopytoWiley.Returninstructionsanda freeofchargereturnmailinglabelareavailableatwww.wiley.com/go/returnlabel.Ifyouhavechosentoadoptthis textbookforuseinyourcourse,pleaseacceptthisbookasyourcomplimentarydeskcopy.OutsideoftheUnited States,pleasecontactyourlocalsalesrepresentative. LibraryofCongressCataloging-in-PublicationData Olinick,Michael. Mathematicalmodelinginthesocialandlifesciences/MichaelOlinick,MiddleburyCollege. pages cm Includesindex. ISBN978-1-118-64269-6(pbk.) 1. Socialsciences—Mathematicalmodels. 2. Lifesciences—Mathematicalmodels. I. Title. H61.O483 2014 300.1'51—dc23 2013044538 PrintedintheUnitedStatesofAmerica 10 9 8 7 6 5 4 3 2 1 Contents Preface viii Acknowledgements xiii 1 Mathematical Models 1 I. Mathematical Systems and Models, 1 II. An Example: Modeling Free Fall, 4 III. Discrete Examples: Credit Cards and Populations, 10 IV. Classification of Mathematical Models, 16 V. Uses and Limitations of Mathematical Models, 18 Exercises, 19 Suggested Projects, 21 2 Stable and Unstable Arms Races 23 I. The Real-World Setting, 23 II. Constructing a Deterministic Model, 25 III. A Simple Model for an Arms Race, 25 IV. The Richardson Model, 28 V. Interpreting and Testing the Richardson Model, 45 VI. Obtaining an Exact Solution, 53 Exercises, 59 Suggested Projects, 63 3 Ecological Models: Single Species 65 I. Introduction, 65 II. The Pure Birth Process, 65 III. Exponential Decay, 71 IV. Logistic Population Growth, 72 V. The Discrete Model of Logistic Growth and Chaos, 80 VI. The Allee Effect, 87 VII. Historical and Biographical Notes, 89 Exercises, 100 Suggested Projects, 104 Biographical References, 105 iii iv CONTENTS 4 Ecological Models: Interacting Species 106 I. Introduction, 106 II. Two Real-World Situations, 106 III. Autonomous Systems, 108 IV. The Competitive Hunters Model, 116 V. The Predator-Prey Model, 123 VI. Concluding Remarks on Simple Models in Population Dynamics, 131 VII. Biographical Sketches, 133 Exercises, 137 Suggested Projects, 139 5 Tumor Growth Models 141 I. Introduction, 141 II. A General Tumor Growth Model, 142 III. The Gompertz Model, 145 IV. Modeling Colorectal Cancer, 155 V. Historical and Biographical Notes, 167 Exercises, 176 Suggested Projects, 177 6 Social Choice and Voting Procedures 179 I. Three Voting Situations, 179 II. Two Voting Mechanisms, 180 III. An Axiomatic Approach, 185 IV. Arrow’s Impossibility Theorem, 187 V. The Liberal Paradox and the Theorem of the Gloomy Alternatives, 191 VI. Instant Runoff Voting, 197 VII. Approval Voting, 203 VIII. Topological Social Choice, 207 IX. Historical and Biographical Notes, 212 Exercises, 224 Suggested Projects, 229 7 Foundations of Measurement Theory 232 I. The Registrar’s Problem, 232 II. What Is Measurement?, 233 III. Simple Measures on Finite Sets, 238 IV. Perception of Differences, 240 V. An Alternative Approach, 242 VI. Some Historical Notes, 245 Exercises, 245 Suggested Projects, 247 Contents v 8 Introduction to Utility Theory 249 I. Introduction, 249 II. Gambles, 250 III. Axioms of Utility Theory, 251 IV. Existence and Uniqueness of Utility, 254 V. Classification of Scales, 257 VI. Interpersonal Comparison of Utility, 259 VII. Historical and Biographical Notes, 261 Exercises, 265 Suggested Projects, 266 9 Equilibrium in an Exchange Economy 268 I. Introduction, 268 II. A Two-Person Economy with Two Commodities, 268 III. An m-Person Economy, 276 IV. Existence of Economic Equilibrium, 283 V. Some Remaining Questions, 293 VI. Historical and Biographical Notes, 294 Exercises, 298 Suggested Projects, 301 VII. Additional Historical and Biographical Notes, 302 10 Elementary Probability 303 I. The Need for Probability Models, 303 II. What Is Probability?, 304 III. A Probabilistic Model, 322 IV. Stochastic Processes, 325 Exercises, 331 Suggested Projects, 335 11 Markov Processes 336 I. Markov Chains, 336 II. Matrix Operations and Markov Chains, 341 III. Regular Markov Chains, 347 IV. Absorbing Markov Chains, 357 V. Historical and Biographical Notes, 369 Exercises, 371 Suggested Projects, 374 vi CONTENTS 12 Two Models of Cultural Stability 375 I. Introduction, 375 II. The Gadaa System, 375 III. A Deterministic Model, 378 IV. A Probabilistic Model, 381 V. Criticisms of the Models, 383 VI. Hans Hoffmann, 384 Exercises, 386 Suggested Projects, 387 13 Paired-Associate Learning 388 I. The Learning Problem, 388 II. The Model, 389 III. Testing the Model, 397 IV. Historical and Biographical Notes, 401 Exercises, 404 Suggested Projects, 406 14 Epidemics 407 I. Introduction, 407 II. Deterministic Models, 411 III. A Probabilistic Approach, 449 IV. Historical and Biographical Notes, 455 Exercises, 459 Suggested Projects, 463 15 Roulette Wheels and Hospital Beds: A Computer Simulation of Operating and Recovery Room Usage 464 I. Introduction, 464 II. The Problems of Interest, 468 III. Projecting the Number of Surgical Procedures, 468 IV. Estimating Operating Room Demands, 469 V. The Simulation Model, 474 VI. Other Examples of Simulation, 480 VII. Historical and Biographical Notes, 484 Exercises, 487 Suggested Projects, 488 Contents vii 16 Game Theory 490 I. Two Difficult Decisions, 490 II. Game Theory Basics, 492 III. The Binding of Isaac, 502 IV. Tosca and the Prisoners’ Dilemma, 507 V. Nash Equilibrium, 511 VI. Dynamic Solutions, 515 VII. Historical and Biographical Notes, 519 Exercises, 522 Suggested Projects, 526 Appendices Appendix I: Sets, 527 Appendix II: Matrices, 531 Appendix III: Solving Systems of Equations, 545 Appendix IV: Functions of Two Variables, 559 Appendix V: Differential Equations, 562 Index 571 Online Chapters (www.wiley.com/college/olinick) 17 Recidivism in the Criminal Justice System 18 Evolutionary Game Theory 19 Agent Based Simulation Preface The goal of this book is to encourage the teaching and learning of mathematical model building relatively early in the undergraduate program. The text introduces the student to a numberofimportantmathematicaltopicsandtoavarietyofmodelsinthesocialsciences,life sciences, and humanities. Students with some mathematical maturity and a strong secondary school background will find many chapters quite accessible. A standard first year calculus course is sufficient background for the remaining chapters. While many of the models use differential equations or some elementary linear algebra, no previous experience with these topics is assumed. The text material will help students gain the necessary knowledge. Appendices on sets, matrices, systems of linear equations, and functions of two variables provide additional background material. Particularproblemsinpoliticalscience,ecology,biology,evolution,medicine,psychol- ogy,sociology,economics,finance,anthropology,criminaljustice,epidemiology,philosophy, religion,opera,andhospitalplanningprovidethemotivationforthedevelopmentoftoolsand techniquesemployedthroughoutappliedmathematics.Theseinclude DifferentialEquations DiscreteDynamicalSystems, Axiomatics ProbabilityTheory RegularMarkovChains AbsorbingMarkovChain MatrixAlgebra LeastSquaresFittingOfData Simulation TheoryOfGames The curricula in many social science and life science disciplines are becoming increas- ingly infused with the development and analysis of formal models. Students in such majors (particularly integrated biology/mathematics and economics/mathematics programs) need an introductiontothemathematicalideasandtechniquesjustlisted.Thistextprovidesonewayof gainingthisexposureinasinglecourse. Iselectedmodelsprimarilyfromthebehavioralsciencesforanumberofreasons: 1. Theyshowtherichvarietyofdisciplinestowhichmathematicsismakingimportant contributions; 2. Because such models require less technical background knowledge than more tra- ditional models in physics, chemistry, and engineering, students can examine in depth many different applications in a one-semester course; viii