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Teacher Note: Module 2 Overview Content Area: Hypothesis-Testing: Cross-Sectional Study


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    1. 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 16, 2011

    2. 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.

    3. 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.

    4. Teacher Note: Photos of Worksheets for Lesson 2-6 2-3d 2-5a 2-3a 2-6a

    5. Start of Lesson 2-6 (estimate 4 class periods)

    6. Review • Big Idea in Lesson 2-5 • Before the study begins, all materials should be ready and all tasks listed and assigned

    7. Lesson 2-6: Conducting Cross-Sectional Studies in Class Study Day

    8. 2-3a - All study planning components should be checked. Study Notebook

    9. 2-5a Study Notebook Assignments for Day of Study All assignments should be made and all plans be in order.

    10. 2-5a, Item 2 - Final Preparation for Each Study Team Enough copies of questionnaire for participants Practice Informed Consent Script I 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. Supplies

    11. Next Class Conducting In-Class Surveys

    12. CDC 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.

    13. Conducting Each Study Study Notebook Have the first study team pass out the questionnaire and proceed with the study steps outlined on the previous slide

    14. CDC Conduct Cross-Sectional Study 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.

    15. Total Study Population Prevalence Rates Honor Roll No Honor Roll Total Healthy Breakfast 70 50 120 No Healthy Breakfast 120 50 70

    16. or 58% Total Study Population Prevalence Rates Honor Roll No Honor Roll Total Healthy Breakfast 70 70 50 120 120 No Healthy Breakfast 120 50 70

    17. or 58% Total Study Population Prevalence Rates Honor Roll No Honor Roll Total Healthy Breakfast 70 70 50 120 120 50 42% or No Healthy Breakfast 120 50 70 120

    18. or 58% Total Study Population Prevalence Ratio Prevalence Rates Honor Roll No Honor Roll Total Healthy Breakfast 70 70 50 120 1.4 120 50 42% or No Healthy Breakfast 120 50 70 120 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.

    19. Next Class Data Analysis

    20. 2-6a Study Notebook Data Management and Calculations for the In-Class Cross-Sectional Study

    21. Next Class Report Out

    22. What are the limitations of these studies?

    23. Mistakes

    24. Guilt by Association

    25. Which happened first?

    26. 2-6a Basis for Report Out and Discussion Study Notebook

    27. Report Out and Discussion of Results In Class 2x2 tables and calculations Accurate statements about results Do the results support the hypothesis? What limitations exist?

    28. Assessment of Simulated Research Experience Teamwork Study Planning Study Conduct Data Management Data Analysis Respect for Participants Report Out Interpretation of Study Study Communications Understanding of Study Strengths and Limitations

    29. Preview of Rubric for Evaluating In-School Studies

    30. Re-Cap • 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

    31. 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

    32. 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

    33. 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

    34. Typical Study Abstract Introduction Methods Results Conclusion

    35. 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.

    36. 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.

    37. Abstract (continued) 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.

    38. “ 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.”