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
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Teacher Note: Module 2 Overview Content Area: Hypothesis-Testing: Cross-Sectional Study Essential Questions: How can I select groups of people and collect.
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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
1Lesson 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.
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Teacher Note: Authentic Assessment for Module 2 of the Epidemiology and the Energy Balance Equation Curriculum
3Lesson 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)
4Lesson 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
6Lesson 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
7Lesson 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?
8Lesson 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
Tied Related
Linked
Things that are associatedare linked in some way that makes them
turn up together.
… associated with each other
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Things that are associated are linked in some way that makes them turn up
together.
Things That Turn Up Together
11Lesson 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
12Lesson 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?
14Lesson 2-1: Looking for Associations
Epidemiologists’ Laboratories
15Lesson 2-1: Looking for Associations
What do epidemiologists look like?
Our Epidemiology Laboratory
16Lesson 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)
17Lesson 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
20Lesson 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
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
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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
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TotalOverweightNot
overweight
Eating junk food
Not eating junk food
Exposure
Outcome / Disease
a b
c d
2x2 Table
What people are in cell a?
cell b?
cell c?
cell d?
26Lesson 2-1: Looking for Associations
TotalOverweightNot
overweight
Eating junk food
Not eating junk food
Exposure
Outcome / Disease
c d
2x2 Table
Is there a comparison group in this 2x2 table?
If yes, where are they?
27Lesson 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
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Exposed
Not Exposed
OutcomeNo
Outcome TotalTests 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
29Lesson 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
30Lesson 2-1: Looking for Associations
a b
dc
2x2 Table
An Apple a Day Keeps the Doctor Away
Total
31Lesson 2-1: Looking for Associations
a b
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
32Lesson 2-1: Looking for Associations
a b
dc
People who are not exposed
dc
2x2 Table
An Apple a Day Keeps the Doctor Away
Total
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An Apple a Day
Infrequent Doctor Visits
No Apple a Day
Frequent Doctor Visits
Lesson 2-1: Looking for Associations
Total
a b
dc
2x2 Table
Study Links Physical Fitness to Academic Achievement
34Lesson 2-1: Looking for Associations
Total
a b
dc
2x2 Table
Study Links Physical Fitness to Academic Achievement
Physically Fit
Lower Grades
Higher Grades
Not Physically Fit
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Total
a b
dc
People who are exposed
a b
2x2 Table
Study Links Physical Fitness to Academic Achievement
Physically Fit
Lower Grades
Higher Grades
Not Physically Fit
36Lesson 2-1: Looking for Associations
a b
dc
2x2 Table
Total
Kids Who Watch R-Rated Movies More Likely to Drink or Smoke
37Lesson 2-1: Looking for Associations
a b
dc
2x2 Table
R-Rated Movies
TotalDrink or Smoke
Kids Who Watch R-Rated Movies More Likely to Drink or Smoke
Do Not Drink or Smoke
No R-Rated
Movies
38Lesson 2-1: Looking for Associations
a b
dc
People who are exposed and have the outcome
a
Total
Kids Who Watch R-Rated Movies More Likely to Drink or Smoke
39Lesson 2-1: Looking for Associations
2x2 Table
R-Rated Movies
Drink or Smoke
Do Not Drink or Smoke
No R-Rated Movies
a b
dc
2x2 Table
Smoking Linked to Youth Eating Disorders
Total
40Lesson 2-1: Looking for Associations
a b
dc
2x2 Table
Smoking Linked to Youth Eating Disorders
Smoke
Eating Disorder
Do Not Smoke
No Eating
Disorder Total
41Lesson 2-1: Looking for Associations
a b
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
42Lesson 2-1: Looking for Associations
a b
dc
2x2 Table
Family Meals Are Good for Mental Health
Total
43Lesson 2-1: Looking for Associations
a b
dc
2x2 Table
Family Meals Are Good for Mental Health
Family Meals
Total
Good Mental Health
Poor Mental
Health
No Family
Meals
44Lesson 2-1: Looking for Associations
a b
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
45Lesson 2-1: Looking for Associations
a b
dc
2x2 Table
Study Links Iron Deficiency to Math Scores
Total
46Lesson 2-1: Looking for Associations
a b
dc
2x2 Table
Study Links Iron Deficiency to Math Scores
Iron Deficiency
Poor Math
Scores
No Iron
Deficiency
Good Math
Scores Total
47Lesson 2-1: Looking for Associations
a b
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
48Lesson 2-1: Looking for Associations
a b
dc
2x2 Table
Proximity of Fast Food Restaurants to Schools and Adolescent Obesity
Total
49Lesson 2-1: Looking for Associations
a b
dc
Proximity of Fast Food Restaurants to Schools and Adolescent Obesity
ObeseNot
Obese Total
50Lesson 2-1: Looking for Associations
2x2 Table
Fast Food Restaurant(s)
Near School
No Fast Food Restaurant(s)
Near School
a b
dc
People who do not have the outcome
d
b
Proximity of Fast Food Restaurants to Schools and Adolescent Obesity
ObeseNot
Obese Total
51
Fast Food Restaurant(s)
Near School
No Fast Food Restaurant(s)
Near School
Lesson 2-1: Looking for Associations
2x2 Table
a b
dc
Total
Higher Risk of Obesity among Teens with More Video Game Playing
52Lesson 2-1: Looking for Associations
2x2 Table
a b
dc
More Video Game
Playing
Obese
Less Video Game
Playing
Not Obese Total
53Lesson 2-1: Looking for Associations
Higher Risk of Obesity among Teens with More Video Game Playing
2x2 Table
a b
dc
ObeseNot
Obese Total
People who are not exposed and have the outcome
c
54Lesson 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
55Lesson 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.