Lesson 2-3: Developing Hypothesis and Study Questions Teacher Note: Module 2 Overview Content Area:...

Lesson 2-3: Developing Hypothesis and Study Questions

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

1Revised Sept 14, 2011


Teacher Note: Enduring Epidemiological Understandings for the Epidemiology and the Energy Balance Equation Curriculum

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

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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.

Lesson 2-3: Developing Hypothesis and Study Questions 4

Teacher Note: Photos of Worksheets for Lesson 2-3

2-3b2-3a 2-3c

2-3d


Start of Lesson 2-3

(estimate 2 class periods)

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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

Review


Overview of Lesson 2-3

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2-3a

Checklist - Study Planning Components and Expectations

2-3Study Hypothesis - Statement of a hypothesized association between an exposure and an outcome

2-3Study Variables - Developing questions about exposure and outcome , and additional questions about participants

2-3Questionnaire - Preparing a one-page sheet that study participants will fill out (typed and copies made)

2-4Draft 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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Notebook

Study


Part of 2-3aExpectations for Successful Completion

of Activities in Lesson 2-3

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Notebook

Study

# Study Plan Component MetSome-what Met

Not Met

2-3Study Hypothesis - Statement of a hypothesized association between an exposure and an outcome1) Stated clearly; 2) makes sense at face value; and 3) is feasible to study in a school setting

□ □ □

2-3Study 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


An educated guess

An unproven idea, based on observation or reasoning, that can be supported or refuted through investigation

A tentative explanation

Hypotheses


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.


• 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

Examples of Variables to Use in a Hypothesis

• 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 night’s 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 night’s sleep - People with high academic performance are more likely to also have more physical activity

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2-3b Notebook

Study

Study Hypothesis

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.

“X is associated with Y”

“People with X are more likely to have Y”

“People with X have higher, or more Y”

How do I state 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 night’s rest

• Other ? ? ?

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2-3b Notebook

Study

Study Hypothesis

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). 18

OPTIONAL SLIDE TO SHOW STUDENTS

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. 19



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 <8 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.

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Possible break point between class periods


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?

012345


Outcome QuestionsTOPIC QUESTION

Fruit ?

Vegetables ?

Fast food ?

Soda ?

Fried potatoes ?

High-sugar foods ?


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 ?

Outcome Questions


TOPIC QUESTION


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 ?

Outcome Questions


TOPIC QUESTION



Fast food Yesterday, how many times did you eat fast food?

Soda ?

Fried potatoes ?

High-sugar foods ?

Outcome Questions


TOPIC QUESTION




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 ?

Outcome Questions


TOPIC QUESTION





Fried potatoes Yesterday, how many servings of French fries, home fries, or hash browns did you eat?

High-sugar foods ?

Outcome Questions


TOPIC QUESTION





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?

Outcome Questions


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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Yes Exposure

Total

No Exposure

a b

c d

Yes Outcome

No Outcome

The 2x2 table

Exposure and Outcome

Distributions Among Individuals in a Study Population

Optional: Use as needed for

review of 2x2 tables and

necessity for a question about

exposure and a question about

outcome

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2-3c

Study Variables: Questions About Exposure and Outcome and

Additional Questions

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Notebook

Study

How should we ask

about eating a healthy

breakfast?


“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

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Notebook

Study

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.)


2-3c

Item 6 – Additional Questions Notebook

Study

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?

Questions to Gather Additional Information on

Participants


Break Between Classes

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2-3d

Sample Questionnaire for for Cross-Sectional Study

Notebook

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


Type your questionnaire

Make enough copies for all

potential study

participants


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

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