Teacher Note: Module 2 Overview Content Area: Hypothesis-Testing: Cross-Sectional Study Essential Questions: How can I select groups of people and collect data/evidence from them that will test my hypothesis? If my causal hypothesis is correct, how would the exposure and outcome be distributed in these groups? Enduring Understanding: Causal hypotheses can be tested by conducting investigations of the exposures and outcomes of selected groups of people as they go about their lives. Information from these observational studies can be used to determine if an exposure and an outcome are associated. Because observational studies are complicated by factors not controlled by the observer, when an association is found, other explanations in addition to causality also must be considered. Core Concepts: Testing hypotheses Association Exposure/outcome Control group 2x2 table Observational studies Study design/study plan Study samples Prevalence rate Prevalence ratio Statement of effect Lessons: 2-1 Looking for Associations 2-2 Cross-Sectional Studies 2-3 Developing Hypothesis and Study Questions 2-4 Respect – Part II 2-5 Planning Study Conduct 2-6 Cross-Sectional Study - In Class 2-7 Cross-Sectional Study – In School 1 Lesson 2-1: Looking for Associations Revised Sept 14, 2011

Teacher Note: Enduring Epidemiological Understandings for the Epidemiology and the Energy Balance Equation Curriculum Lesson 2-1: Looking for Associations 1.Health and disease are not distributed haphazardly in a population. There are patterns to their occurrence that can be identified through surveillance. Analysis of the patterns of health and disease distribution can provide clues for formulating hypotheses about their possible causes. 2.Causal hypotheses can be tested by conducting investigations of the exposures and outcomes of selected groups of people as they go about their lives. Information from these observational studies can be used to determine if an exposure and an outcome are associated. Because observational studies are complicated by factors not controlled by the observer, other explanations also must be considered. 2

Teacher Note: Authentic Assessment for Module 2 of the Epidemiology and the Energy Balance Equation Curriculum 3 Lesson 2-1: Looking for Associations Students will conduct, analyze, and interpret observational, cross- sectional studies among students in their class and then among students outside their class. Working in teams, students will have the opportunity to demonstrate their abilities to select a reasonable hypothesis of interest to them, design study questions about exposure and outcome, obtain informed consent, collect and manage data, calculate and compare prevalence rates, make accurate statements about whether their data support that hypothesis, and consider alternate explanations for what they observed. Reporting of results will be required, such as a written report, an item for the school newspaper, or an oral presentation or poster for students, teachers, and/or parents. Specific performance criteria will be used to help ensure that the experiences allow a genuine, realistic, and fair assessment of students’ comprehension of the Module 2 Enduring Epidemiological Understanding.

Start of Lesson 2-1 (estimate 2 class periods) 4 Lesson 2-1: Looking for Associations

Big Ideas in Module 1 Review 5 Descriptive epidemiology studies patterns of health events and behaviors in populations. Surveys are a useful tool for assessing patterns of health behaviors in youth. Understanding patterns of health behaviors in youth helps to generate hypotheses to explain those patterns.

Hypotheses about associations Generate Module 1 – Descriptive epidemiology: You studied patterns of disease and health-related events and behaviors, and used the information to generate hypotheses about why these patterns exist. Test Bridge between the Two Sides of Epidemiology 6 Lesson 2-1: Looking for Associations Module 2 – Analytical epidemiology: You will test hypotheses by examining potential connections (associations) between health-related exposures and outcomes.

Hypothesis Module 1 Descriptive Epidemiology Module 2 Analytical Epidemiology An Example About the Energy Balance Equation Description of the increase in teenage overweight Description of increases in teenagers eating junk food Hypothesis: Eating junk food can cause teenagers to become overweight Scientific studies of the association between teenagers eating junk food and their weight status 7 Lesson 2-1: Looking for Associations Hypotheses about associations Generate Test

Association Found between Lack of a Good Night’s Sleep and Obesity What does “association” mean? 8 Lesson 2-1: Looking for Associations

Association Found between Lack of a Good Night’s Sleep and Obesity 9 What does it mean? Make a statement about what it means when we say that two things are associated with each other, such as in the headline, "Association Found between Lack of a Good Night’s Sleep and Obesity." Lesson 2-1: Looking for Associations

What do we mean when we say that there is an association between two things? Associated TiedRelated Linked Things that are associated are linked in some way that makes them turn up together. … associated with each other 10 Lesson 2-1: Looking for Associations

Things that are associated are linked in some way that makes them turn up together. Things That Turn Up Together 11 Lesson 2-1: Looking for Associations

Suicide Higher in Areas with Guns Smoking Linked to Youth Eating Disorders Snacks Key to Kids’ TV- Linked Obesity: China Study Family Meals Are Good for Mental Health Students Who Bring Their Lunch to School Eat Less Junk Food Higher Risk of Obesity Among Teens with More Video-Game Playing Breakfast Each Day May Keep Colds Away Study Concludes: Movies Influence Youth Smoking Study Links Iron Deficiency to Math Scores Study Links Physical Fitness to Academic Achievement Proximity of Fast Food Restaurants to Schools and Adolescent Obesity Things That Turn Up Together 12 Lesson 2-1: Looking for Associations

13 Exposures and Outcomes in Analytical Studies... What kinds of exposures and outcomes are studied? Exposures  A health-related behavior  A health-related event  A lifestyle or socioeconomic factor  A chemical or physical exposure  Psychological stress  Something else with which one comes in contact Outcomes  A health-related behavior  Infectious disease  Chronic disease  Trauma, Injury  Any other temporary or permanent health condition Lesson 2-1: Looking for Associations

How do we conduct these analytical studies? 14 Lesson 2-1: Looking for Associations

Epidemiologists’ Laboratories 15 Lesson 2-1: Looking for Associations What do epidemiologists look like?

Our Epidemiology Laboratory 16 Lesson 2-1: Looking for Associations

Naturally occurring circumstances in which groups of people within a population have been exposed to different levels of the hypothesized cause of an outcome. Natural Experiments (unplanned) 17 Lesson 2-1: Looking for Associations

18 Natural Experiments (unplanned) Lesson 2-1: Looking for Associations

Planned Observational Studies of Natural Experiments 19 An epidemiological study of a natural experiment in which the investigator is not involved in the intervention other than to record, classify, count, and analyze results. Lesson 2-1: Looking for Associations

In-Class and In-School Observational Studies of Natural Experiments 20 Lesson 2-1: Looking for Associations

21 Questions About Conducting Analytical Studies... What kinds of skills and interests are needed to conduct analytical epidemiology studies? Interest in investigations and solving mysteries Critical thinking Analytical/mathematical skills Enjoyment in working with people Team player How do analytical studies answer health-related questions? Collect information on exposures and outcomes from individuals in populations, in order to identify potential health- related associations Lesson 2-1: Looking for Associations

22 Association Two things linked in some way that makes them turn up together Hypothesis An educated guess - an unproven idea, based on an observation that can be supported or refuted through investigation Exposure Something that impacts a person and is suspected of causing an effect; something with which a person comes in contact; Outcome The result of an exposure Natural Experiment Naturally occurring circumstances in which groups of people within a population have been exposed to different levels of the hypothesized cause of an outcome. Observational Study An epidemiological study of a natural experiment - in which the investigator is not involved in any intervention, other than to record, classify, count, and analyze results. Review of Common Words Used in Analytical Epidemiology

23 Possible break point between class periods Lesson 2-1: Looking for Associations

The 2x2 table is a tool used to express the number of people with and without the exposure and with and without the outcome. An Important Tool in Analytical Epidemiology The 2x2 Table 24 Lesson 2-1: Looking for Associations

A cross-classification of data where categories of one variable are presented in rows and categories of another variable are presented in columns. The simplest contingency table is the 2x2 table Contingency Table 25 Lesson 2-1: Looking for Associations

Total Overweight Not overweight Eating junk food Not eating junk food ExposureExposure Outcome / Disease ab cd 2x2 Table What people are in cell a? cell b? cell c? cell d? 26 Lesson 2-1: Looking for Associations

Total Overweight Not overweight Eating junk food Not eating junk food ExposureExposure Outcome / Disease cd 2x2 Table Is there a comparison group in this 2x2 table? If yes, where are they? 27 Lesson 2-1: Looking for Associations

People who participate in a study and do not have the exposure of interest People whose results are compared to the group that was exposed Comparison Group 28 Lesson 2-1: Looking for Associations

Exposed Not Exposed Outcome No Outcome Total Tests hypotheses Analytic Epidemiology Summary So Far... Includes an unexposed comparison group Can use a 2x2 table to explore a possible association between exposure and outcome 29 Lesson 2-1: Looking for Associations

Suicide Higher in Areas with Guns Smoking Linked to Youth Eating Disorders Higher Risk of Obesity among Teens with More Video-Game Playing Family Meals Are Good for Mental Health Students who bring their lunch to school eat less junk food Study Links Spanking to Aggression Breakfast Each Day May Keep Colds Away Study Concludes: Movies Influence Youth Smoking Study Links Iron Deficiency to Math Scores Study Links Physical Fitness to Academic Achievement Pollution Linked with Birth Defects in US Study Things That Turn Up Together Proximity of Fast Food Restaurants to Schools and Adolescent Obesity 30 Lesson 2-1: Looking for Associations

ab dc 2x2 Table An Apple a Day Keeps the Doctor Away Total 31 Lesson 2-1: Looking for Associations

ab dc 2x2 Table An Apple a Day Keeps the Doctor Away An Apple a Day Infrequent Doctor Visits No Apple a Day Frequent Doctor Visits Total 32 Lesson 2-1: Looking for Associations

ab dc People who are not exposed dc 2x2 Table An Apple a Day Keeps the Doctor Away Total 33 An Apple a Day Infrequent Doctor Visits No Apple a Day Frequent Doctor Visits Lesson 2-1: Looking for Associations

Total ab dc 2x2 Table Study Links Physical Fitness to Academic Achievement 34 Lesson 2-1: Looking for Associations

Total ab dc 2x2 Table Study Links Physical Fitness to Academic Achievement Physically Fit Lower Grades Higher Grades Not Physically Fit 35 Lesson 2-1: Looking for Associations

Total ab dc People who are exposed ab 2x2 Table Study Links Physical Fitness to Academic Achievement Physically Fit Lower Grades Higher Grades Not Physically Fit 36 Lesson 2-1: Looking for Associations

ab dc 2x2 Table Total Kids Who Watch R-Rated Movies More Likely to Drink or Smoke 37 Lesson 2-1: Looking for Associations

ab dc 2x2 Table R-Rated Movies Total Drink or Smoke Kids Who Watch R-Rated Movies More Likely to Drink or Smoke Do Not Drink or Smoke No R-Rated Movies 38 Lesson 2-1: Looking for Associations

ab dc People who are exposed and have the outcome a Total Kids Who Watch R-Rated Movies More Likely to Drink or Smoke 39 Lesson 2-1: Looking for Associations 2x2 Table R-Rated Movies Drink or Smoke Do Not Drink or Smoke No R-Rated Movies

ab dc 2x2 Table Smoking Linked to Youth Eating Disorders Total 40 Lesson 2-1: Looking for Associations

ab dc 2x2 Table Smoking Linked to Youth Eating Disorders Smoke Eating Disorder Do Not Smoke No Eating Disorder Total 41 Lesson 2-1: Looking for Associations

ab dc People who are exposed and do not have the outcome b 2x2 Table Smoking Linked to Youth Eating Disorders Smoke Eating Disorder Do Not Smoke No Eating Disorder Total 42 Lesson 2-1: Looking for Associations

ab dc 2x2 Table Family Meals Are Good for Mental Health Total 43 Lesson 2-1: Looking for Associations

ab dc 2x2 Table Family Meals Are Good for Mental Health Family Meals Total Good Mental Health Poor Mental Health No Family Meals 44 Lesson 2-1: Looking for Associations

ab dc People who are not exposed and do not have the outcome d 2x2 Table Family Meals Are Good for Mental Health Family Meals Total Good Mental Health Poor Mental Health No Family Meals 45 Lesson 2-1: Looking for Associations

ab dc 2x2 Table Study Links Iron Deficiency to Math Scores Total 46 Lesson 2-1: Looking for Associations

ab dc 2x2 Table Study Links Iron Deficiency to Math Scores Iron Deficiency Poor Math Scores No Iron Deficiency Good Math Scores Total 47 Lesson 2-1: Looking for Associations

ab dc People who do not have the outcome and are not exposed d 2x2 Table Study Links Iron Deficiency to Math Scores Iron Deficiency Poor Math Scores No Iron Deficiency Good Math Scores Total 48 Lesson 2-1: Looking for Associations

ab dc 2x2 Table Proximity of Fast Food Restaurants to Schools and Adolescent Obesity Total 49 Lesson 2-1: Looking for Associations

ab dc Proximity of Fast Food Restaurants to Schools and Adolescent Obesity Obese Not Obese Total 50 Lesson 2-1: Looking for Associations 2x2 Table Fast Food Restaurant(s) Near School No Fast Food Restaurant(s) Near School

ab dc People who do not have the outcome d b Proximity of Fast Food Restaurants to Schools and Adolescent Obesity Obese Not Obese Total 51 Fast Food Restaurant(s) Near School No Fast Food Restaurant(s) Near School Lesson 2-1: Looking for Associations 2x2 Table

ab dc Total Higher Risk of Obesity among Teens with More Video Game Playing 52 Lesson 2-1: Looking for Associations 2x2 Table

ab dc More Video Game Playing Obese Less Video Game Playing Not Obese Total 53 Lesson 2-1: Looking for Associations Higher Risk of Obesity among Teens with More Video Game Playing 2x2 Table

ab dc Obese Not Obese Total People who are not exposed and have the outcome c 54 Lesson 2-1: Looking for Associations More Video Game Playing Less Video Game Playing Higher Risk of Obesity among Teens with More Video Game Playing 2x2 Table

Module 2 Enduring Understanding 55 Lesson 2-1: Looking for Associations 2.Causal hypotheses can be tested by conducting investigations of the exposures and outcomes of selected groups of people as they go about their lives. Information from these observational studies can be used to determine if an exposure and an outcome are associated. Because observational studies are complicated by factors not controlled by the observer, when an association is found, other explanations in addition to causality also must be considered Kid-Friendly Translation: Illness and health may be linked to one or more causes. Using groups of people, we can study possible causes related to our daily lives, such as choices about what we do, and where we live and work. When we find a link between health/illness and such a factor, it might be a causal link, but we also have to consider other explanations for the connection.

Big Ideas in Lesson 2-1 Two things are associated when they “turn up together.” Epidemiologists study associations. Descriptive epidemiology generates hypotheses about associations and analytical epidemiology tests hypotheses about associations. A common way to test hypotheses is with an observational study of a natural experiment. The 2x2 table is a useful tool for numerically expressing associations between exposure and outcome in a group of individuals. Re-Cap 56 Lesson 2-1: Looking for Associations