Teacher Note: Module 2 Overview

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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
Revised Sept 14, 2011
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Teacher Note Enduring Epidemiological
Understandings for the Epidemiology and the
Energy Balance Equation Curriculum  

•  
• 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.
• 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
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.
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Teacher Note Photos of Worksheets for Lesson
2-3
2-3a
2-3b
2-3c
2-3d
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Start of Lesson 2-3 (estimate 2 class periods)
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Review

• Big Ideas in Lesson 2-2
• The cross-sectional design is an observational
  study
  of a natural experiment
• This design is relatively quick and simple,
  asking individuals about exposure and outcome at
  one point in time
• After the prevalence is calculated for the group
  with the exposure, the next question is compared
  to what?
• The compared to what consists of prevalence for
  the unexposed controls
• Dividing one prevalence by the other produces
  the prevalence ratio it tells us if/how the
  exposure and outcome are associated
• Because exposure and outcome are measured at the
  same point in time, it is usually not possible to
  determine the time order of the exposure and the
  outcome (which came first) and as such, the
  association may not be interpretable

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Overview of Lesson 2-3
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2-3a
Checklist - Study Planning Components
and Expectations
2-3 Study Hypothesis - Statement of a hypothesized association between an exposure and an outcome
2-3 Study Variables - Developing questions about exposure and outcome , and additional questions about participants
2-3 Questionnaire - Preparing a one-page sheet that study participants will fill out (typed and copies made)
2-4 Draft Informed Consent Script - Preparing a script to be read to possible study participants (typed and copies made)
2-5 Plans for Study Conduct Having assignments for study day
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Part of 2-3a
Expectations for Successful Completion
of Activities in
Lesson 2-3
Study Plan Component Met Some-what Met Not Met
2-3 Study Hypothesis - Statement of a hypothesized association between an exposure and an outcome 1) Stated clearly 2) makes sense at face value and 3) is feasible to study in a school setting ? ? ?
2-3 Study Variables - Developing questions about exposure and outcome 1) Clear questions that will mean the same thing to anyone who reads it 2) a good description of what you are trying to measure 3) a good understanding of challenges in measurement and 4) an awareness of other information about study participants that will help in understanding study results
2-3 Questionnaire - Preparing a one-page sheet that study participants will fill out (typed and copies made) Format of the survey that is user-friendly and clear in presenting questions and answer options and instructions
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Hypotheses
An educated guess
A tentative explanation
An unproven idea, based on observation or
reasoning, that can be supported or refuted
through investigation
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Hypotheses?

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Hypotheses?
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Tips

• Your hypothesis statement should state the
  hypothesized relationship between an exposure
  variable and an outcome variable, including the
  direction expected.
• Make sure that the hypothesis you choose is of
  genuine interest to you, because you will be
  spending your time and energy exploring
  it.
• Your stated hypothesis MUST NOT require the
  collection of any information that might be
  considered embarrassing, sensitive, or illegal.
• The hypothesis needs to be related to nutrition
  and/or physical activity.

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Examples of Variables to Use in a Hypothesis

• Eat school cafeteria food
• Regularly watch TV
• Have a sedentary lifestyle
• Have a high-fat diet
• Take multivitamins
• Eat breakfast
• Have perception of overweight
• Have good academic performance
• Regularly play computer games
• Eat junk food every day

• Have a low-fat diet
• Regularly exercise
• Participate in a team sport
• Eat fruits and vegetables
• Drink high calorie drinks
• Drink diet soda
• Walk to school
• Get a good nights rest
• Other ? ? ?

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Some variables can be an exposure or an outcome
When is eating more fruits and vegetables an
exposure? When is eating more fruits and
vegetables an outcome? Examples of
Hypotheses - People who eat more fruits and
vegetables take more multivitamins - People who
rarely watch TV are more likely to eat fruits and
vegetables When is having more physical
activity an exposure? When is having more
physical activity an outcome? Examples of
Hypotheses - Physical activity is associated
with a longer nights sleep - People with high
academic performance are more likely to also
have more physical activity
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2-3b
How do I state a hypothesis?
Study Hypothesis
X is associated with Y People with X are more
likely to have Y People with X have higher, or
more Y
Why is your study team interested in testing this
hypothesis? Discuss the reason(s) your team
thinks it will be possible to
test this hypothesis in your class and school.
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2-3b
Study Hypothesis

• Eat school cafeteria food
• Regularly watch TV
• Have a sedentary lifestyle
• Have a high-fat diet
• Take multivitamins
• Eat breakfast
• Have perception of overweight
• Have good academic performance
• Regularly play computer games
• Eat junk food every day

• Have a low-fat diet
• Regularly exercise
• Participate in a team sport
• Eat fruits and vegetables
• Drink high calorie drinks
• Drink diet soda
• Walk to school
• Get a good nights rest
• Other ? ? ?

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A few examples of hypotheses to test

• Students who drink caffeinated drinks do more
  homework after school.
• Students who drink caffeinated drinks get less
  sleep.
• Healthy eating (at least 2 servings of fruit and
  vegetables a day) results in better grades
  (doing well in school.
• Students that regularly eat vegetables have
  fewer periods of illness (24 hours or more of
  flu/cold symptoms).
• Students who eat breakfast have fewer colds and
  therefore have fewer absences from school.
• A healthy breakfast is associated with playing
  in an organized sport.
• Students who eat dinner with their family more
  often get better grades.
• Students who skip lunch will eat more snacks.
• People who eat more fruits and vegetables take
  more multivitamins.
• Drinking more water is associated with eating
  more fruits and vegetables.
• Students who drink more sweetened drinks are
  more likely to eat unhealthy snacks.
• Drinking at least 2 cans or a 20 ounce bottle of
  non-diet soda per day leads to a crash (feeling
  tired).

OPTIONAL SLIDE TO SHOW STUDENTS
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A few examples of hypotheses to test

• Students who have one or more cats or dogs are
  more physically active.
• Students who have one or more cats or dogs have
  more school absences due to colds.
• Receiving a daily, weekly, or monthly allowance
  is related to eating junk food/unhealthy food
  more than twice a day.
• Students who chew gum eat fewer snacks.
• Students who listen to an IPOD are more likely
  to participate in physical activity.
• Students who text more are less physically
  active.
• Watching more TV is associated with having lower
  stress levels.
• Students who watch TV eat more snacks.
• Students who regularly play video games eat more
  snacks.
• Students who play regular video games (not
  active) eat more junk food.
• Playing active video games is related to getting
  better grades.
• Student athletes, on average, get more sleep
  than students who do not participate in a sport.

OPTIONAL SLIDE TO SHOW STUDENTS
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A few examples of hypotheses to test

• Students who participate in sports are more
  satisfied with their lives
• Physical activity is associated with eating less
  junk food.
• People who participate in a team sport are more
  likely to eat fruits and vegetables.
• Physically active students place greater weight
  on the importance of a healthy lifestyle.
• Regular exercise is related to higher academic
  performance.
• Students who get 8 or more hours of sleep on
  average have higher academic performance.
• Students who sleep lt8 hours a night eat more
  often than those who get at least 8 hours of
  sleep.
• Students who have less parental supervision are
  more likely to watch TV.
• Students who have less parental supervision eat
  more junk food for after school snacks.
• High academic performance is associated with more
  physical activity.
• High academic performance is associated with a
  healthy diet.

OPTIONAL SLIDE TO SHOW STUDENTS
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Possible break point between class periods
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More Information about CHIS Study

• Theresa A. Hastert, Susan H. Babey. School lunch
  source and adolescent dietary behavior.
  Prevention of Chronic Diseases 2009, Vol 6 (4).
• http//www.cdc.gov/pcd/issues/2009/oct/08_0182.htm

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Review Criteria for a Good Question

• It should be clear and unambiguous, written so
  that its intended audience understands it.
• It should mean the same thing to everyone who
  reads it.
• The answer options must categorize and cover the
  entire range of possible behavior (from complete
  absence of the behavior to a maximum amount of
  the behavior).
• The time period to consider when answering a
  particular question must be appropriate (long or
  short enough) to capture the frequency of
  behavior desired (depending on the information
  desired and the type of behavior).

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Exposure Question
During the school year, about how many times a
week do you usually bring your own lunch to
school from home? 0 1 2 3 4 5
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Outcome Questions
TOPIC QUESTION
Fruit ?
Vegetables ?
Fast food ?
Soda ?
Fried potatoes ?
High-sugar foods ?
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Outcome Questions
TOPIC QUESTION
Fruit Yesterday, how many servings of fruit, such as an apple or a banana, did you eat?
Vegetables ?
Fast food ?
Soda ?
Fried potatoes ?
High-sugar foods ?
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Outcome Questions
TOPIC QUESTION
Fruit Yesterday, how many servings of fruit, such as an apple or a banana, did you eat?
Vegetables Yesterday, how many servings of vegetables, like corn, green beans, green salad or other vegetables did you eat?
Fast food ?
Soda ?
Fried potatoes ?
High-sugar foods ?
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Outcome Questions
TOPIC QUESTION
Fruit Yesterday, how many servings of fruit, such as an apple or a banana, did you eat?
Vegetables Yesterday, how many servings of vegetables, like corn, green beans, green salad or other vegetables did you eat?
Fast food Yesterday, how many times did you eat fast food?
Soda ?
Fried potatoes ?
High-sugar foods ?
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Outcome Questions
TOPIC QUESTION
Fruit Yesterday, how many servings of fruit, such as an apple or a banana, did you eat?
Vegetables Yesterday, how many servings of vegetables, like corn, green beans, green salad or other vegetables did you eat?
Fast food Yesterday, how many times did you eat fast food?
Soda Yesterday, how many glasses or cans of soda, such as Coke, or other sweetened drinks, such as fruit punch or Sunny Delight did you drink? Do not count diet drinks.
Fried potatoes ?
High-sugar foods ?
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Outcome Questions
TOPIC QUESTION
Fruit Yesterday, how many servings of fruit, such as an apple or a banana, did you eat?
Vegetables Yesterday, how many servings of vegetables, like corn, green beans, green salad or other vegetables did you eat?
Fast food Yesterday, how many times did you eat fast food?
Soda Yesterday, how many glasses or cans of soda, such as Coke, or other sweetened drinks, such as fruit punch or Sunny Delight did you drink? Do not count diet drinks.
Fried potatoes Yesterday, how many servings of French fries, home fries, or hash browns did you eat?
High-sugar foods ?
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Outcome Questions
TOPIC QUESTION
Fruit Yesterday, how many servings of fruit, such as an apple or a banana, did you eat?
Vegetables Yesterday, how many servings of vegetables, like corn, green beans, green salad or other vegetables did you eat?
Fast food Yesterday, how many times did you eat fast food?
Soda Yesterday, how many glasses or cans of soda, such as Coke, or other sweetened drinks, such as fruit punch or Sunny Delight did you drink? Do not count diet drinks.
Fried potatoes Yesterday, how many servings of French fries, home fries, or hash browns did you eat?
High-sugar foods Yesterday, how many servings of high-sugar foods, such as cookies, candy, doughnuts, pastries, cake or popsicles did you eat?
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Questions for your Cross-Sectional Studies

• One question must obtain information about the
  exposure in your hypothesis and the other
  question must obtain information about the
  outcome in your hypothesis.
• The study information on exposure and outcome
  must fit into a 2x2 table.
• A yes/no question will fit and is recommended.
• If using a multiple choice question, you will
  need a predetermined cut point so there is a
  higher/lower range to fit into the 2x2 table.

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The 2x2 table
Optional Use as needed for review of 2x2
tables and necessity for a question about
exposure and a question about outcome
Exposure and Outcome Distributions Among
Individuals in a
Study Population
Yes Outcome
No Outcome
Total
a
b
Yes Exposure
c
d
No Exposure
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2-3c
Study Variables Questions About

Exposure and Outcome and Additional
Questions
How should we ask about eating a healthy
breakfast?
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Criteria for a Good Question

• It should be clear and unambiguous, written so
  that its intended audience understands it.
• It should mean the same thing to everyone who
  reads it.
• The answer options must categorize and cover the
  entire range of possible behavior (from complete
  absence of the behavior to a maximum amount of
  the behavior).
• The time period to consider when answering a
  particular question must be appropriate (long or
  short enough) to capture the frequency of
  behavior desired (depending on the information
  desired and the type of behavior).

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2-3c
Item 5 - Labeling a 2x2 Table
2x2 Table Fill in the two boxes in the table
below, to show how your exposure and outcome
variables will be analyzed in a contingency table
in order to test your hypothesis. (Note if
you plan to use multiple choice questions for
your exposure and/or outcome, determine cut
points for the data so that you can fill in the
contingency table below.)
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2-3c
Item 6 Additional Questions
Questions to Gather

Additional Information on Participants  
Think about what other information about students
in your study would be interesting
to know, in terms of your hypothesis.
(Hint perhaps gender would be one of
these) In the space below, write any additional
questions for your questionnaire that will gather
information about these other characteristics of
your study subjects.   .
Should we ask about gender?
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Break Between Classes
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2-3d
Sample Questionnaire for

for Cross-Sectional Study
Thank you for your participation in this survey.
Please answer the questions below by circling one
choice for each question. When you are
finished, fold this paper in half and follow
instructions for handing in your
questionnaire.   Remember Do not write your name
anywhere on this paper.    Study Questions
(Circle one answer for each question)    1.
During the past month, did you usually eat 2 or
more servings of fruits/vegetables per day?
Yes No    2. In the last semester
that you have completed, did you have a grade
average of A or B?
Yes No 3. What is your gender? Male
Female   4. What grade are you in? 6th
grade 7th grade 8th grade  
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Type your questionnaire Make enough copies for
all potential study participants
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Re-Cap

• Big Ideas in Lesson 2-3
• A good study plan includes
  careful thought about
  choice of
  exposure and outcome variables and high-quality
  questions to measure them
• Additional questions about other characteristics
  of participants can be asked in order to better
  understand study results
• A well-planned study has a user-friendly
  questionnaire to administer to participants