Skip to main content

To Be Healthy, Wealthy, and Wise: Using Decision Modeling to Personalize Policy in Health, Hunger Relief, and Education

  • Chapter
  • First Online:
Women in Industrial and Systems Engineering

Abstract

Decision-making to satisfy the basic human needs of health, food, and education is complex, accomplishing this in such a way that solutions are personalized to the needs of the individual has been the focus of my research. This chapter will present an overview of my research with several of my former students in the area of decision-making under conditions of uncertainty with a focus on human-centric decision problems in three primary areas: health care, humanitarian logistics, and education. This research seeks to inform decision-making with the goal of improving decision quality. To this end, this research utilizes and develops theory in the areas of Markov decision processes (MDPs), semi-Markov decision processes (SMDPs), partially observable Markov decision processes (POMDPs), optimization, simulation, and Bayesian decision analysis to address these real-world problems. This research has made an impact on how researchers and practitioners address complex societal issues, such as health disparities, public health preparedness, hunger relief, student performance, and personalized medical decision-making.

This is a preview of subscription content, log in via an institution to check access.

Access this chapter

Chapter
USD 29.95
Price excludes VAT (USA)
  • Available as PDF
  • Read on any device
  • Instant download
  • Own it forever
eBook
USD 129.00
Price excludes VAT (USA)
  • Available as EPUB and PDF
  • Read on any device
  • Instant download
  • Own it forever
Hardcover Book
USD 169.99
Price excludes VAT (USA)
  • Durable hardcover edition
  • Dispatched in 3 to 5 business days
  • Free shipping worldwide - see info

Tax calculation will be finalised at checkout

Purchases are for personal use only

Institutional subscriptions

References

  • American Diabetes Association (2017) Pharmacologic approaches to glycemic treatment. In: Standards of medical care in diabetes-2017. pp S64–S74

    Google Scholar 

  • Anderson G, Horvath J (2004) The growing burden of chronic disease in America. Public Health Rep (Washington, DC: 1974) 119(3):263–270

    Article  Google Scholar 

  • Badrick E, Renehan AG (2014) Diabetes and cancer: 5 years into the recent controversy. Eur J Cancer 50(12):2119–2125

    Article  Google Scholar 

  • Bertsimas D, Sim M (2004) The price of robustness. Oper Res 52(1):35–53

    Article  MathSciNet  Google Scholar 

  • Boyd CM, Fortin M (2010) Future of multimorbidity research: how should understanding of multimorbidity inform health system design? Public Health Rev 32(2):451–474

    Article  Google Scholar 

  • Brailsford SC (2007) Proceedings of the 2007 winter simulation conference. In: Henderson SG, Biller B, Hsieh M-H, Shortle J, Tew JD, Barton RR (eds). pp 1436–1448

    Google Scholar 

  • Bristow PJ, Hillman KM, Chey T et al (2000) Rates of in-hospital arrests, deaths and intensive care admissions: the effect of a medical emergency team. Med J Aust 173:236–240

    Google Scholar 

  • Buist MD, Moore GE, Bernard SA et al (2002) Effects of a medical emergency team on reduction of incidence of and mortality from unexpected cardiac arrests in hospital: preliminary study. Br Med J 324(7334):387–390

    Article  Google Scholar 

  • Bynd S, Sen A, Subbe C, Gemmell L (2004) Modified early warning score: one for all and A&E? Br J Anaesth 92(4):611P–612P

    Google Scholar 

  • Capan M, Ivy JS, Rohleder T, Hickman J, Huddleston JM (2015a) Individualizing and optimizing the use of early warning scores in acute medical care for deteriorating hospitalized patients. Resuscitation 93:107–112. https://doi.org/10.1016/j.resuscitation.2014.12.032

    Article  Google Scholar 

  • Capan M, Ivy JS, Wilson JR, Huddleston JM (2015b) A stochastic model of acute-care decisions based on patient and provider heterogeneity. Health Care Manag Sci 20(2):187–206. https://doi.org/10.1007/s10729-015-9347-x

    Article  Google Scholar 

  • Capan M, Wu P, Campbell M, Mascioli S, Jackson EV (2017) Using electronic health records and nursing assessment to redesign clinical early recognition systems. Health Syst 6(2):112–121

    Article  Google Scholar 

  • Caughey G, Roughead E, Roughead EE (2011) Multimorbidity research challenges: where to go from here? J Comorb 1(1):8–10

    Article  Google Scholar 

  • CDC/NCHS (2010) National hospital discharge survey, 2000–2010. http://www.cdc.gov/nchs/data/databriefs/db118.htm

  • Chan PS, Jain R, Nallmothu BK et al (2010) Rapid response teams: a systematic review and meta-analysis. Arch Intern Med 170:18–26

    Article  Google Scholar 

  • Chang C-H, Lin J-W, Wu L-C, Lai M-S, Chuang L-M (2012) Oral insulin secretagogues, insulin, and cancer risk in type 2 diabetes mellitus. J Clin Endocrinol Metab 97(7):E1170–E1175

    Article  Google Scholar 

  • Committee on Quality of Health Care in America, Institute of Medicine (2001) Crossing the quality chasm: a new health system for the 21st century. National Academies Press, Washington, DC

    Google Scholar 

  • Confrey J, Maloney A (2010) The construction, refinement, and early validation of the equipartitioning learning trajectory. In: Proceedings of the 9th international conference of the learning sciences, Chicago, vol 1, pp 968–975

    Google Scholar 

  • Cox CE, Wysham NG (2015) Untangling health trajectories among patients with sepsis. Ann Am Thorac Soc 12(6):796–797

    Article  Google Scholar 

  • Czura C (2011) Merinoff symposium 2010: sepsis—speaking with one voice. Mol Med 17(1–2):2–3

    Article  Google Scholar 

  • DeVita MA, Bellomo R, Hillman K, Kellum J, Rotondi A, Teres D, Auerbach A, Chen W, Duncan K, Kenward G, Bell M, Buist M, Chen J, Bion J, Kirby A, Lighthall G, Ovreveit J, Braithwaite RS, Gosbee J, Milbrandt E, Peberdy M, Savitz L, Young L, Harvey M, Galhotra S (2006) Findings of the first consensus conference on medical emergency teams. Crit Care Med 34:2463–2478

    Article  Google Scholar 

  • Esper AM, Moss M, Lewis CA, Nisbet R, Mannino DM, Martin GS (2006) The role of infection and comorbidity: factors that influence disparities in sepsis. Crit Care Med 34(10):2576–2582

    Article  Google Scholar 

  • FBCENC (2018) Food Bank of Central & Eastern North Carolina. http://www.foodbankcenc.org/site/PageServer?pagename=FBCENCHome. Accessed 2018

  • Feeding America (2018). https://hungerandhealth.feedingamerica.org/. Accessed 2018

  • Food and Agriculture Organization of the United Nations (2018). http://www.fao.org/state-of-food-security-nutrition/en/

  • Franciosi M, Lucisano G, Lapice E, Strippoli GFM, Pellegrini F, Nicolucci A (2013) Metformin therapy and risk of cancer in patients with type 2 diabetes: systematic review. PLoS One 8(8):1–12

    Article  Google Scholar 

  • Geraci JM, Escalante CP, Freeman JL, Goodwin JS (2005) Comorbid disease and cancer: the need for more relevant conceptual models in health services research. J Clin Oncol 23(30):7399–7404

    Article  Google Scholar 

  • Gerteis J, Izrael D, Deitz D, LeRoy L, Ricciardi R, Miller T et al (2014) Multiple chronic conditions chartbook. Agency for Healthcare Research and Quality, Rockville

    Google Scholar 

  • Giovannetti ER, Wolff JL, Xue Q-L, Weiss CO, Leff B, Boult C et al (2012) Difficulty assisting with health care tasks among caregivers of multimorbid older adults. J Gen Intern Med 27(1):37–44

    Article  Google Scholar 

  • Gray L, Smyth K, Palmer R, Zhu X, Callahan J (2002) Heterogeneity in older people: examining physiologic failure, age, and comorbidity. J Am Geriatr Soc 50(12):1955–1961

    Article  Google Scholar 

  • Hamilton BE, Martin JA, Osterman MJK, Driscoll AK, Rossen LM (2017) Births: provisional data for 2016. NVSS Vital Statistics Rapid Release 2(2):1–21. https://www.cdc.gov/nchs/data/vsrr/report002.pdf

  • Harper LM, Caughey AB, Odibo AO, Roehl KA, Zhao Q, Cahill AG (2012) Normal progress of induced labor. Obstet Gynecol 119(6):1113–1118. https://doi.org/10.1097/AOG.0b013e318253d7aa

    Article  Google Scholar 

  • Hayes AJ, Leal J, Gray AM, Holman RR, Clarke PM (2013) UKPDS outcomes model 2: a new version of a model to simulate lifetime health outcomes of patients with type 2 diabetes mellitus using data from the 30 year United Kingdom Prospective Diabetes Study: UKPDS 82. Diabetologia 56(9):1925–1933

    Article  Google Scholar 

  • Hicklin K (2016) Decision models for mode of delivery combining patient and clinician risk perceptions and preferences. North Carolina State University

    Google Scholar 

  • Hicklin K, Ivy J, Cobb Payton F, Viswanathan M, Myers E (2018) Exploring the value of waiting during labor. Serv Sci 10(3):334–353. https://doi.org/10.1287/serv.2018.0205

    Article  Google Scholar 

  • Hillman K (2008) Rapid response systems. Indian J Crit Care 12(2):77–81

    Article  Google Scholar 

  • Howard R (1960) Dynamic programming and Markov processes. M.I.T. Press, Cambridge

    MATH  Google Scholar 

  • Institute of Safe Medication Practices (2010) National survey on drug shortages reveals serious impact of patient safety [WWW document]. http://www.ismp.org/pressroom/PR20100923.pdf. Accessed 19 Feb 2012

  • Iskander KN, Osuchowski MF, Stearns-Kurosawa DJ, Kurosawa S, Stepien D, Valentine C et al (2013) Sepsis: multiple abnormalities, heterogeneous responses, and evolving understanding. Physiol Rev 93(3):1247–1288

    Article  Google Scholar 

  • Karlstad O, Starup-Linde J, Vestergaard P, Hjellvik V, Bazelier MT, Schmidt MK et al (2013) Use of insulin and insulin analogs and risk of cancer—systematic review and meta-analysis of observational studies. Curr Drug Saf 8(5):333–348

    Article  Google Scholar 

  • Kerr EA, Heisler M, Krein SL, Kabeto M, Langa KM, Weir D et al (2007) Beyond comorbidity counts: how do comorbidity type and severity influence diabetes patients’ treatment priorities and self-management? J Gen Intern Med 22(12):1635–1640

    Article  Google Scholar 

  • Kohn LT, Corrigan JM, Donaldson MS (1999) To err is human: building a safer health system. National Academy Press: Institute of Medicine Report, Washington

    Google Scholar 

  • Liu V, Escobar GJ, Greene JD, Soule J, Whippy A, Angus DC et al (2014) Hospital deaths in patients with sepsis from 2 independent cohorts. JAMA 312(1):90

    Article  Google Scholar 

  • Loeb DF, Binswanger IA, Candrian C, Bayliss EA (2015) Primary care physician insights into a typology of the complex patient in primary care. Ann Fam Med 13(5):451–455

    Article  Google Scholar 

  • Ludikhuize J, Smorenburg SM, de Rooij SE et al (2012) Identification of deteriorating patients on general wards; measurement of vital parameters and potential effectiveness of the modified early warning score. J Crit Care 27(4):424.e7–424.13

    Article  Google Scholar 

  • Maddigan SL, Feeny DH, Johnson JA (2005) Health-related quality of life deficits associated with diabetes and comorbidities in a Canadian National Population Health Survey. Qual Life Res 14(5):1311–1320

    Article  Google Scholar 

  • Mannucci PM, Nobili A, REPOSI Investigators (2014) Multimorbidity and polypharmacy in the elderly: lessons from REPOSI. Intern Emerg Med 9(7):723–734

    Article  Google Scholar 

  • Marengoni A, Onder G (2015) Guidelines, polypharmacy, and drug-drug interactions in patients with multimorbidity. BMJ (Clinical Research Ed) 350(4):h1059

    Google Scholar 

  • Mazze RS, Strock ES, Bergenstal RM, Criego A, Cuddihy R, Langer O et al (2011) Staged diabetes management. Wiley-Blackwell, Oxford

    Book  Google Scholar 

  • McGloin H, Adam SK, Singer M (1999) Unexpected deaths and referrals to intensive care of patients on general wards. are some cases potentially avoidable? J R Coll Physicians Lond 33:255–259

    Google Scholar 

  • Nataraj N (2017) Modeling for the care of complex patients. North Carolina State University, Raleigh

    Google Scholar 

  • Nataraj N, Ivy JS, Payton FC, Norman J (2018) Diabetes and the hospitalized patient: a cluster analytic framework for characterizing the role of sex, race and comorbidity from 2006 to 2011. Health Care Manag Sci 21(4):534–553

    Article  Google Scholar 

  • Nation’s Report Card (2015) The nation’s report card: mathematics. https://www.nations reportcard.gov/reading_math_2015/#?grade=4. Acceseed 2.1.2018

  • National Academy of Engineering (2018) NAE grand challenges for engineering in the 21st century: advance personalized learning. http://www.engineeringchallenges.org/challenges/learning.aspx. Accessed 2.1.2018

  • National Academy of Sciences, National Academy of Engineering & Institute of Medicine (2007) Rising above the gathering storm: energizing and employing America for a brighter economic future. The National Academies Press, Washington, DC

    Google Scholar 

  • National Center for Education Statistics (2006) The nation’s report card: mathematics 2005. http://nces.ed.gov/nationsreportcard/pdf/main2005/2006453.pdf. Accessed 2.1.2018

  • National Research Council Center for Education: Mathematics Learning Study Committee (2001) Adding it up: helping children learn mathematics. The National Academies Press, Washington, DC

    Google Scholar 

  • National Science Board (2007) National action plan for addressing the critical needs of U.S. science, technology, engineering, and mathematics education system. http://www.nsf.gov/nsb/documents/2007/stem_action.pdf. Accessed 2.1.2018

  • North Carolina Education Research Data Center (2018) Homepage. Duke University Center for Child and Family Policy. https://childandfamilypolicy.duke.edu/research/nc-education-data-center/. Accessed 2.1.2018

  • Nunes BP, Flores TR, Mielke GI, Thumé E, Facchini LA (2016) Multimorbidity and mortality in older adults: a systematic review and meta-analysis. Arch Gerontol Geriatr 67:130–138

    Article  Google Scholar 

  • Piette J, Kerr E (2006) The impact of comorbid chronic conditions on diabetes care. Diabetes Care 29(3):725–731

    Article  Google Scholar 

  • Prytherch DR, Smith GB, Schmidt PE, Featherstone PI (2010) ViEWS—towards a national early warning score for detecting adult inpatient deterioration. Resuscitation 81(8):932–937

    Article  Google Scholar 

  • Public Schools of North Carolina (2018a) North Carolina end-of-grade tests at grades 3-8. http://www.ncpublicschools.org/accountability/testing/eog/. Accessed 2.1.2018

  • Public Schools of North Carolina (2018b) ABC program information. http://www.dpi.state.nc.us/accountability/reporting/abc/2000-01/history. Accessed 2.1.2018

  • Public Schools of North Carolina (2018c) Educator effectiveness model: EVAAS. http://www.ncpublicschools.org/effectiveness-model/evaas/. Accessed 2.1.2018

  • Puterman ML (1994) Markov decision processes: discrete stochastic dynamic programming. Wiley-Interscience, New York

    Book  Google Scholar 

  • Reamer A (2012) Characterizing the progression of performance in mathematics over time: the application of Markovian models to an education system. Doctoral Dissertation. Retrieved from North Carolina State University Libraries: http://www.lib.ncsu.edu/resolver/1840.16/8728. Accessed 2.1.2018

  • Reamer A, Ivy J, Vila-Parrish A, Young R (2015) Understanding the evolution of mathematics performance in primary education and the implications for STEM learning: a Markovian approach. Comput Hum Behav 47:4–17

    Article  Google Scholar 

  • Royal College of Physicians (2012) National early warning score (NEWS): standardizing the assessment of acute illness severity in the NHS. Report of a working party. RCP, London

    Google Scholar 

  • Safford MM, Allison JJ, Kiefe CI (2007) Patient complexity: more than comorbidity. The vector model of complexity. J Gen Intern Med 22(Suppl 3):382–390

    Article  Google Scholar 

  • Schaink A, Kuluski K, Lyons R, Fortin M (2012) A scoping review and thematic classification of patient complexity: offering a unifying framework. J Comorb 2(1):1–9

    Article  Google Scholar 

  • Sengul Orgut I (2015) Modeling for the equitable and effective distribution of food donations under capacity constraints. Doctoral dissertation. https://repository.lib.ncsu.edu/bitstream/handle/1840.16/10469/etd.pdf?sequence=2

  • Sengul Orgut I, Ivy JS, Uzsoy R, Wilson JR (2015) Modeling for the equitable and effective distribution of donated food under capacity constraints. IIE Trans 48(3):252–266

    Article  Google Scholar 

  • Sengul Orgut I, Ivy JS, Uzsoy R (2017) Modeling for the equitable and effective distribution of food donations under stochastic receiving capacities. IISE Trans 49(6):567–578

    Article  Google Scholar 

  • Sengul Orgut I, Ivy JS, Uzsoy R, Hale C (2018) Robust optimization approaches for the equitable and effective distribution of donated food. Eur J Oper Res 269(2):516–531

    Article  Google Scholar 

  • Simon M, Tzur R (2004) Explicating the role of mathematical tasks in conceptual learning: an elaboration of the hypothetical learning trajectory. Math Think Learn 6(2):91–104

    Article  Google Scholar 

  • Singer M, Deutschman CS, Seymour CW, Shankar-Hari M, Annane D, Bauer M et al (2016) The third international consensus definitions for sepsis and septic shock (Sepsis-3). JAMA 315(8):801–810

    Article  Google Scholar 

  • Smallwood R (1971) The analysis of economic teaching strategies for a simple learning model. J Math Psychol 8:285–301

    Article  Google Scholar 

  • Smith AF, Wood J (1998) Can some in-hospital cardio-respiratory arrests be prevented? A prospective survey. Resuscitation 37:133–137

    Article  Google Scholar 

  • Smith GB, Prytherch DR, Schmidt P et al (2006) Hospital-wide physiological surveillance—a new approach to the early identification and management of the sickpatient. Resuscitation 71:19–28

    Article  Google Scholar 

  • Smith KN, Vila-Parrish AR, Ivy JS, Abel SR (2016) A simulation approach for evaluating medication supply chain structures. Int J Syst Sci Oper Logist 4(1):13–26

    Google Scholar 

  • Subbe C, Kruger M, Rutherford P, Gemmel L (2001) Validation of a modified early warning score in medical admissions. QJM 94(10):521–526

    Article  Google Scholar 

  • Taffel SM, Placek PJ, Liss T (1987) Trends in the United States cesarean section rate and reasons for the 1980-85 rise. Am J Public Health 77(8):955–959

    Article  Google Scholar 

  • Tejada JJ, Diehl K, Ivy JS, Wilson JR, King RE, Ballan MJ et al (2013) Combined DES/SD simulaton model of breast cancer screening for older women: an overview. In: 2013 winter simulations conference (WSC). IEEE, pp 41–53

    Google Scholar 

  • Tejada JJ, Ivy JS, King RE, Wilson JR, Ballan MJ, Kay MG et al (2014) Combined DES/SD model of breast cancer screening for older women, II: screening-and-treatment simulation. IIE Trans 46(7):707–727

    Article  Google Scholar 

  • Tsilidis KK, Kasimis JC, Lopez DS, Ntzani EE, Ioannidis JPA (2015) Type 2 diabetes and cancer: umbrella review of meta-analyses of observational studies. BMJ 350:g7607

    Article  Google Scholar 

  • United States Census Bureau (2016) Small area income and poverty estimates. http://www.census.gov/did/www/saipe/data/interactive/saipe.html?s_appname=saipe&map_yearselector=2014&map_geoselector=aa_c&s_appName=saipe&map_yearSelector=2014&map_geoSelector=aa_c. Accessed 2016

  • United States Department of Agriculture (2018). https://www.ers.usda.gov/topics/food-nutrition-assistance/food-security-in-the-us/measurement.aspx

  • United States Department of Education (2008) Foundations for success: the final report of the national mathematics advisory panel. http://www2.ed.gov/about/bdscomm/list/mathpanel/report/final-report.pdf. Accessed 2.1.2018

  • Vila-Parrish AR, Ivy JS, King RE (2008) A simulation based approach for inventory modeling of perishable pharmaceuticals. In: Proceedings of the winter simulation conference, pp 1532–1538

    Google Scholar 

  • Vila-Parrish AR, Ivy JS, King R, Abel SR (2012) Patient-based pharmaceutical inventory management: a two-stage inventory and production model for perishable products with Markovian demand. Health Syst 1(1):69–83

    Article  Google Scholar 

  • Vila-Parrish AR, Ivy JS, He B (2015) Impact of the influenza season on a hospital from a pharmaceutical inventory management perspective. Health Syst 4(1):12–28. Special Issue: Public Health Preparedness; Abingdon

    Article  Google Scholar 

  • Vincent JL, Opal SM, Marshall JC, Tracey KJ (2013) Sepsis definitions: time for change. Lancet 381(9868):774–775

    Article  Google Scholar 

  • Vogeli C, Shields AE, Lee TA, Gibson TB, Marder WD, Weiss KB et al (2007) Multiple chronic conditions: prevalence, health consequences, and implications for quality, care management, and costs. J Gen Intern Med 22(S3):391–395

    Article  Google Scholar 

  • Wachter RM, Pronovost PJ (2006) The 100,000 lives campaign: a scientific and policy review. Jt Comm J Qual Patient Saf 32(11):621–627

    Article  Google Scholar 

  • Wang HE, Shapiro NI, Griffin R, Safford MM, Judd S, Howard G et al (2012) Chronic medical conditions and risk of sepsis. PLoS One 7(10):e48307. Gold JA (ed)

    Article  Google Scholar 

  • Ward BW, Schiller JS, Goodman RA (2014) Multiple chronic conditions among US adults: a 2012 update. Prev Chronic Dis 11:E62

    Google Scholar 

  • Wolff JL, Starfield B, Anderson G et al (2002) Prevalence, expenditures, and complications of multiple chronic conditions in the elderly. Arch Intern Med 162(20):2269

    Article  Google Scholar 

  • World Health Organization Human Reproduction Programme, 10 April 2015 (2015) WHO statement on caesarean section rates. Reprod Health Matters 23(45):149–150. https://doi.org/10.1016/j.rhm.2015.07.007

  • Zhang J, Landy HJ, Branch DW, Burkman R, Haberman S, Gregory KD, Hatjis CG et al (2010a) Contemporary patterns of spontaneous labor with normal neonatal outcomes. Obstet Gynecol 116(6):1281–1287

    Article  Google Scholar 

  • Zhang J, Troendle J, Reddy UM, Laughon SK, Branch DW, Burkman R, Landy HJ et al (2010b) Contemporary cesarean delivery practice in the United States. Am J Obstet Gynecol 203(4):326.e1–326.e10. https://doi.org/10.1016/j.ajog.2010.06.058. Elsevier Inc.

    Article  Google Scholar 

  • Zhang S, Payton FC, Ivy JS (2013) Characterizing the impact of mental disorders on HIV patient length of stay and total charges. IIE Trans Healthcare Syst Eng 3(3):139–146

    Article  Google Scholar 

  • Zimmerman E, Woolf S, Haley A (2015) Understanding the relationship between education and health. U.S. Department of Health and Human Services Agency for Healthcare Research and Quality. https://www.ahrq.gov/professionals/education/curriculum-tools/population-health/zimmerman.html. Accessed 2.1.2018

Download references

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Julie Simmons Ivy .

Editor information

Editors and Affiliations

Rights and permissions

Reprints and permissions

Copyright information

© 2020 Springer Nature Switzerland AG

About this chapter

Check for updates. Verify currency and authenticity via CrossMark

Cite this chapter

Ivy, J.S. et al. (2020). To Be Healthy, Wealthy, and Wise: Using Decision Modeling to Personalize Policy in Health, Hunger Relief, and Education. In: Smith, A. (eds) Women in Industrial and Systems Engineering. Women in Engineering and Science. Springer, Cham. https://doi.org/10.1007/978-3-030-11866-2_11

Download citation

  • DOI: https://doi.org/10.1007/978-3-030-11866-2_11

  • Published:

  • Publisher Name: Springer, Cham

  • Print ISBN: 978-3-030-11865-5

  • Online ISBN: 978-3-030-11866-2

  • eBook Packages: EngineeringEngineering (R0)

Publish with us

Policies and ethics