Lesson 2-6: Cross-Sectional Study – In Class Teacher Note: Module 2 Overview Content Area: Hypothesis-Testing: Cross-Sectional Study Essential Questions:

Lesson 2-6: Cross-Sectional Study – In Class

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 16, 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.

2


Teacher Note: Authentic Assessment for Module 2 of the Epidemiology and the Energy Balance Equation Curriculum

3

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 2-6: Cross-Sectional Study – In Class 4

Teacher Note: Photos of Worksheets for Lesson 2-6

2-5a2-3a 2-3d

2-6a


Start of Lesson 2-6

(estimate 4 class periods)

5


Big Idea in Lesson 2-5

• Before the study begins, all materials should be ready and all tasks listed and assigned

Review


Lesson 2-6: Conducting Cross-Sectional Studies in Class

Study Day

7


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

8

Notebook

Study

2-3a - All study planning components should be checked.


All

assignments

should be

made and

all plans

be in

order.

2-5a

Assignments for Day of Study Notebook

Study


2-5a, Item 2 - Final Preparation for Each Study Team

10

Supplies

Practice

Informed Consent ScriptI am about to give you a Question / Answer

Form on which a question is written. Do not

write your name on the form. I am going to

ask you to answer the question by circling

your answer with a No. 2 pencil and then

immediately folding the form in half so that

no one else can see your answer. You do

not need to answer the question. If you do

not wish to participate, simply fold the form

in half. Your participation is voluntary,

anonymous, and confidential. Let me repeat

– You are not required to participate and

nothing will happen to you if you do not. I

will pass several large envelops around the

class into which you can place your folded

form regardless of whether or not you

answered the question.

Enough copies of questionnaire for participants


Next Class

Conducting In-Class Surveys


2-5a, Item 3 - Conduct Cross-Sectional Studies In-Class One at a Time

One at a time, each study team will do the following:• 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.

CDC

12


Conducting Each Study

Have the first study

team pass out the

questionnaire and

proceed with the

study steps outlined

on the previous slide

Notebook

Study


Conduct Cross-Sectional Study In-Class One at a Time

CDC

14

One at a time, each study team will do the following:• 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.


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.


Next Class

Data Analysis


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

20

2-6a Notebook

Study

Lesson 2-6: Cross-Sectional Study – In Class21

Next Class

Report Out


What are the limitations of these studies?


Mistakes


Guilt by Association


Which happened first?


2-6a Basis for Report Out and Discussion

26

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

27


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


Preview of Rubric for Evaluating In-School Studies

29

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


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

Re-Cap


Optional additional session

As appropriate for your class, and as time allows, use these few additional slides from

the CHIS study article to stimulate discussion about limitations of their studies

and cross-sectional studies in general


As appropriate for your class, and as time allows, use these few additional slides from

the CHIS study article to stimulate discussion about limitations of their studies

and cross-sectional studies in general


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

33


Typical Study Abstract

Introduction

Methods

Results

Conclusion


Abstract

IntroductionAs rates of childhood obesity rise, the nutritional content of lunches eaten at school is more heavily scrutinized. We examined the association between dietary behaviors and the number of days that adolescents bring lunch to school.

MethodsWe analyzed cross-sectional data for 2,774 adolescents who responded to the 2005 California Health Interview Survey and reported dietary behaviors for a weekday.


Abstract (continued)ResultsIn bivariate analyses, adolescents who typically brought their lunch from home 5 days per week ate fast food on fewer occasions; consumed fewer servings of soda, fried potatoes, and high-sugar foods; and ate more fruit and vegetables compared with adolescents who never brought their lunch to school. In linear regressions controlling for demographics, body mass index, desire to change weight, parent education, and adult presence after school, students who typically brought their lunch to school 5 days per week ate fast food 0.35 fewer times and consumed 0.35 fewer servings of soda, 0.10 fewer servings of fried potatoes, 0.25 fewer servings of high-sugar foods, and 0.95 more servings of fruit and vegetables per day compared with students who never brought their lunch to school.


ConclusionThese findings suggest that adolescents who bring lunch to school from home have more positive dietary behaviors than do adolescents who get their lunches from other sources. Improving the nutritional quality of foods offered from other sources, such as the National School Lunch Program and competitive foods, could help improve adolescent dietary behaviors.

Abstract (continued)


“ 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.”

Lesson 2-6: Cross-Sectional Study – In Class Teacher Note: Module 2 Overview Content Area: Hypothesis-Testing: Cross-Sectional Study Essential Questions:

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