lesson 2-7: cross-sectional study – in school teacher note: module 2 overview content area:...

Lesson 2-7: Cross-Sectional Study – In School

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 2-7: Cross-Sectional Study – In School 4

Teacher Note: Photos of Worksheets for Lesson 2-7

2-5a2-3a 2-3d

2-7a 2-7b 2-7c


Teacher Note: Cross-Sectional Study - In School

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Start of Lesson 2-7

(estimate 4 class periods)

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Big Ideas in Lesson 2-6

• The in-class studies are final practice for conducting the in-school studies.

• This is simulated research, not actual research, because the results are not generalizable.

• Steps and materials should all be ready prior to starting.

• In all aspects of the study, every effort should be made to protect the privacy of participants and their information.

• The study allows us to test a hypothesis: it yields counts, that can be turned into prevalence rates, that can be compared as a prevalence ratio, that provides information about an association versus no association.

Review


Rubric for Evaluating In-School Study and Poster

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Criteria Got It Getting It Will Get It SoonParticipation All study team

members participateMost study team members participate

Some study team members participate

Use of Epidemiology Terminology such as Prevalence, Prevalence Ratio, and others

All are appropriate and accurate

Most are appropriate and accurate

Some are appropriate and accurate

Understanding of Importance of Informed Consent

Full understanding of importance

Some understanding of importance

Limited understanding of importance

Thoughtful discussion of challenges in data collection and management

At least 2 challenges well discussed

One challenge well discussed

Little discussion of challenges

Accurate calculation of prevalence and prevalence ratio

All prevalence rates and ratios correctly calculated

Some correctly calculated

Mostly or completely incorrectly calculated

Thoughtful discussion of whether the data support or do not support the hypothesis

A thorough and reasonable discussion of whether the data support the hypothesis

Some reasonable thoughts about whether the data support the hypothesis

Little thoughtful discussion of whether the data support the hypothesis

Understanding of limitations of their study

Identified at least 2 reasonable and logical limitations

Identified 1 reasonable and logical limitation

Did not identify any reasonable or logical limitations


Lesson 2-7: Cross-Sectional Study - In School

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Preparation for In-School Cross-Sectional Studies

Who is going to be in your study population among all the students in your school?

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Preparation for In-School Cross-Sectional Studies

Any other tweaks or adjustments based on experience from your in-

class study?

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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

Notebook

Study

2-3a

Checklist - Study Planning

Components and Expectations

Consider adjustments to improve the quality of your study.

Lesson 2-7: Cross-Sectional Study – In School13

Consider

re-assignments

as appropriate,

based on

experience during the

in-class study.

2-5a

Assignments for Day of Study Notebook

Study


Next Class

Conducting In-School Surveys


Putting It All Together on Study Day

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Conduct Steps for Study Held in Each Class

CDC

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• Introduce team

• Read informed consent statement and remind class of their right to not participate.

• Review questionnaire with the entire class

+ Read over all the questions

+ Remind them to NOT write their name on the paper

• Instruct participants to voluntarily and anonymously fill out the questionnaire.

• When they are finished, instruct students to fold their paper in half and to put the paper into the large envelope that will be passed around (participants and non-participants should do this)

• Thank participants.


Next Class

Data Analysis


Data Management and Calculations for the In-School Cross-Sectional Study

2-7a Notebook

Study


In-School Cross-Sectional Study: Analysis by Gender

OPTIONAL - 2-7b Notebook

Study


Honor RollTotal

12070 50

No Honor Roll

120No Healthy Breakfast 7050

Healthy Breakfast

Prevalence Rates

Total Study Population


Honor RollTotal

12070 50

No Honor Roll

70

120or 58%


Healthy Breakfast

Prevalence Rates



Honor RollTotal

12070 50

No Honor Roll

70

120or 58%

120No Healthy Breakfast 7050 or

Healthy Breakfast

Prevalence Rates

50

12042%



Honor RollTotal

12070 50

No Honor Roll

70

120or 58%


Prevalence Ratio

or

Healthy Breakfast

Prevalence Rates

50

12042%

1.4


Students who eat a healthy breakfast are 1.4 times as likely to make the honor role compared to students who do not eat a healthy breakfast.


Honor RollTotal

6040 20

No Honor Roll


Healthy Breakfast

Prevalence Rates

Males Only


Honor RollTotal

6040 20

No Honor Roll

40

60or 67%


Healthy Breakfast

Prevalence Rates

Males Only


Honor RollTotal

6040 20

No Honor Roll

40

60or 67%


Healthy Breakfast

Prevalence Rates

10

4025%

Males Only


Honor RollTotal

6040 20

No Honor Roll

40

60or 67%


Prevalence Ratio

or

Healthy Breakfast

Prevalence Rates

10

4025%

2.7

Males Only

Boys who eat a healthy breakfast are 2.7 times as likely to make the honor role compared to boys who do not eat a healthy breakfast.


Honor RollTotal

6030 30

No Honor Roll


Healthy Breakfast

Prevalence Rates

Females Only


Honor RollTotal

6030 30

No Honor Roll

30

60or 50%


Healthy Breakfast

Prevalence Rates

Females Only


Honor RollTotal

6030 30

No Honor Roll

30

60or 50%


Healthy Breakfast

Prevalence Rates

40

8050%

Females Only


Honor RollTotal

6030 30

No Honor Roll

30

60or 50%


Prevalence Ratio

or

Healthy Breakfast

Prevalence Rates

40

8050%

1.0

Females Only

Girls who eat a healthy breakfast are 1.0 times as likely to make the honor role compared to girls who do not eat a healthy breakfast.


Interpretation of Analysis by Gender

Boys who eat a healthy breakfast are 2.7 times as likely to make the honor role compared to boys who do not eat a healthy breakfast.

Girls who eat a healthy breakfast are 1.0 times as likely to make the honor role compared to girls who do not eat a healthy breakfast.

What do these findings suggest?


Next Class

Reporting Out

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2-7a – Basis for Report Out and Discussion Notebook

Study


1. 2x2 tables and calculations

2. Accurate statements about results

3. Do the results support the hypothesis?

4. What limitations exist?

Report Out and Discussion of Results In Class

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Interpretation of Prevalence Ratios

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Results Interpretation

Prevalence Ratio At or Near 1.0

NO ASSOCIATION – the prevalence rate among the exposed group is similar or the same as the prevalence rate among the unexposed group

Prevalence Ratio Above 1.0

POSITIVE ASSOCIATION - the prevalence rate among the exposed group is greater than the prevalence rate among the unexposed group

Prevalence Ratio Below 1.0

NEGATIVE ASSOCIATION the prevalence rate among the exposed group is lower than the prevalence rate among the unexposed group

• A prevalence ratio of 1.1 is a weak positive association, while a prevalence ratio of 3.1 is a strong positive association

• A prevalence ratio of 0.95 is a weak negative association, while a ratio of 0.45 is a strong negative association


“ This study has several limitations.”

“The dietary intake data are self-reported, making them subject to errors.”

“A single question was used to address each dietary behavior, and questions ask about diet on the previous day, which might not be representative of the respondents’ overall diet patterns.”

“Additionally, we did not assess or control for the social desirability of bringing lunch.”

An important limitation of the cross-sectional study design is that exposure and outcome are measured at the same point in time - - can we tell the time order?


2-7c

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Notebook

Study

Rubric for Poster of In-School Study Results


Assessment of Simulated Research Experience

Study PlanningTeamwork

Report Out

Respect for Participants

Study Conduct

Understanding of Study Strengths and Limitations

Data Analysis

Interpretation

of Study

Data Management

Study Communications


Big Ideas in Lesson 2-7

• Same big ideas as in Lesson 2-7.• The independent (to the extent

possible) conduct of an in-school study by the study team constitutes an authentic assessment of their knowledge and skills related to the second 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, other explanations also must be considered.

Re-Cap


Optional - A Little History

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Examples from Pioneer Epi Club Members 8th Graders at Charles J. Riley School 9 Paterson, New Jersey – Spring

20101. Epi Stars - Drinking at least 2 cans or a 20 ounce bottle of

non-diet soda every day leads to a crash (feeling tired) - Prevalence ratio = 2.5

2. Pop Science – A healthy breakfast is associated with playing in an organized sport - Prevalence ratio = 0.96

3. Hypertensions – Receiving a daily, weekly, or monthly allowance is related to eating junk food/unhealthy food more than twice a day - Prevalence ratio = 1.6

4. Dr. Observation – Healthy eating (at least 2 servings of fruit and vegetables a day) results in better grades (“doing well in school”) - Prevalence ratio = 1.0


Making a Poster to Display Survey Results

Examples on next slides from Epi Club Members 8th Graders at Charles J. Riley School 9

Paterson, New Jersey – Spring 2011

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lesson 2-7: cross-sectional study – in school teacher note: module 2 overview content area:...

Documents

crosssectional studies

design study questions

planning study conduct

causal hypothesis

school teacher note

developing hypothesis

causal hypotheses

reasonable hypothesis