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Study Designs Dr. Abdulmohsen Alzalabani MBChB, ABCM, MSc(Epi), MHPE Assistant Professor, Community Medicine Chairman, Med...
Research? the process of answering a question by appropriately collected data What is the frequency of a disease in a cert...
Research question?
<ul><li>Is anise effective in prevention of Influenza? </li></ul><ul><li>هل اليانسون مفيد للوقاية من الانفلونزا؟ </li></ul>
Define your question <ul><li>Anise: </li></ul><ul><ul><li>Which Anise? </li></ul></ul><ul><ul><li>Frequency? </li></ul></u...
Exposure/Intervention and Outcome Intervention Exposure Anise Mobile phones Outcome Outcome Influenza Brain Cancer
So, how to answer the question?
Mr. Ali is a 50 years old taxi driver in Riyadh. ……………… .. ……………… .. ……………… .. He reported that he drink a cup of Anise ev...
A group of people aging between 40 and 50 years working as taxi drivers in Riyadh. ……………… .. ……………… .. ……………… .. They repo...
 
Population Random Sample Drinking Anise Not drinking Anise Cross-sectional Study (Survey) All measured at the same time In...
Cross-sectional studies (surveys) <ul><li>are the simplest type of epidemiological study </li></ul><ul><li>information is ...
EXAMPLE : Survey of current headache With headache No headache Total Students in this class
EXAMPLE : Survey of current headache With headache No headache Total Students in this class 5 45 50 Prevalence =  5 50 = 0...
Population People without Flu Drinking Anise Not drinking Anise Influenza No Influenza Influenza No Influenza Follow-up Co...
Population People without disease Exposed Unexposed Disease No disease Disease No disease Follow-up Cohort Study
Population Influenza patients People with no Influenza Anise drinker No Anise Anise drinker No Anise Case-Control Study As...
Population Cases (disease) Control (No disease) Exposed Not Exposed Exposed Not Exposed Case-Control Study Ask about the p...
What was the role of the researcher? Observing only Observational Studies Case-control Cohort Cross-sectional Case-series ...
 
Experimental studies Normal people Give “Anise” Influenza No Influenza Before-after Problems? Follow-up
Experimental studies Normal people Give “Anise” Influenza No Influenza Controlled Trial Problems? Normal people Give “Noth...
Experimental studies Normal people Give “Anise” Influenza No Influenza Randomized Controlled Trial (RCT) Problems? Normal ...
How do you go about designing a study? <ul><li>Decide which is the outcome and which is the (primary) exposure </li></ul><...
General concerns with all types of studies <ul><li>Clear definitions of exposure and outcome </li></ul><ul><li>Use valid/r...
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Study designs med_students

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Transcript of "Study designs med_students"

  1. 1. Study Designs Dr. Abdulmohsen Alzalabani MBChB, ABCM, MSc(Epi), MHPE Assistant Professor, Community Medicine Chairman, Medical Education Department College of Medicine, Taibah University
  2. 2. Research? the process of answering a question by appropriately collected data What is the frequency of a disease in a certain place at a certain time? What caused this disease? Descriptive Hypothesis generation Hypothesis testing the process of developing a list of possible candidates for the “causes”
  3. 3. Research question?
  4. 4. <ul><li>Is anise effective in prevention of Influenza? </li></ul><ul><li>هل اليانسون مفيد للوقاية من الانفلونزا؟ </li></ul>
  5. 5. Define your question <ul><li>Anise: </li></ul><ul><ul><li>Which Anise? </li></ul></ul><ul><ul><li>Frequency? </li></ul></ul><ul><ul><li>Quantity? </li></ul></ul><ul><li>Treatment: </li></ul><ul><ul><li>Cure? </li></ul></ul><ul><ul><li>Relief of symptoms? </li></ul></ul><ul><ul><li>Reduce duration? </li></ul></ul><ul><ul><li>Reduce complication? </li></ul></ul><ul><li>Prevention: </li></ul><ul><ul><li>Prevention of infection? </li></ul></ul><ul><ul><li>Prevention of disease? </li></ul></ul><ul><ul><li>Prevention of complications? </li></ul></ul>
  6. 6. Exposure/Intervention and Outcome Intervention Exposure Anise Mobile phones Outcome Outcome Influenza Brain Cancer
  7. 7. So, how to answer the question?
  8. 8. Mr. Ali is a 50 years old taxi driver in Riyadh. ……………… .. ……………… .. ……………… .. He reported that he drink a cup of Anise everyday. He claimed he never caught flu since he started drinking Anise. Case-report Problems? Anecdotal evidence
  9. 9. A group of people aging between 40 and 50 years working as taxi drivers in Riyadh. ……………… .. ……………… .. ……………… .. They reported that they drink a cup of Anise everyday. They claimed they never caught flu since they started drinking Anise. Case-series Problems? Anecdotal evidence
  10. 11. Population Random Sample Drinking Anise Not drinking Anise Cross-sectional Study (Survey) All measured at the same time Influenza No Influenza
  11. 12. Cross-sectional studies (surveys) <ul><li>are the simplest type of epidemiological study </li></ul><ul><li>information is collected from each subject at one point in time </li></ul><ul><li>information can be on outcomes (e.g. diseases, infections, high blood pressure, low birthweight) </li></ul><ul><li>information can be on exposures (e.g. smoking, diet, occupation) </li></ul><ul><li>information can be on both outcomes and exposures (e.g. HIV positivity and injecting-drug use). </li></ul>
  12. 13. EXAMPLE : Survey of current headache With headache No headache Total Students in this class
  13. 14. EXAMPLE : Survey of current headache With headache No headache Total Students in this class 5 45 50 Prevalence = 5 50 = 0.10 or 10%
  14. 15. Population People without Flu Drinking Anise Not drinking Anise Influenza No Influenza Influenza No Influenza Follow-up Cohort Study
  15. 16. Population People without disease Exposed Unexposed Disease No disease Disease No disease Follow-up Cohort Study
  16. 17. Population Influenza patients People with no Influenza Anise drinker No Anise Anise drinker No Anise Case-Control Study Ask about the past
  17. 18. Population Cases (disease) Control (No disease) Exposed Not Exposed Exposed Not Exposed Case-Control Study Ask about the past
  18. 19. What was the role of the researcher? Observing only Observational Studies Case-control Cohort Cross-sectional Case-series Cross-sectional Case-report Descriptive Studies Analytic Studies Prevalence Distribution Description Testing Association Difference
  19. 21. Experimental studies Normal people Give “Anise” Influenza No Influenza Before-after Problems? Follow-up
  20. 22. Experimental studies Normal people Give “Anise” Influenza No Influenza Controlled Trial Problems? Normal people Give “Nothing” Influenza No Influenza Follow-up
  21. 23. Experimental studies Normal people Give “Anise” Influenza No Influenza Randomized Controlled Trial (RCT) Problems? Normal people Give “Nothing” Influenza No Influenza Normal people randomize Follow-up
  22. 24. How do you go about designing a study? <ul><li>Decide which is the outcome and which is the (primary) exposure </li></ul><ul><li>Is the outcome rare? </li></ul><ul><li>Is the exposure rare? </li></ul><ul><li>Any existing, useful, databases? </li></ul>
  23. 25. General concerns with all types of studies <ul><li>Clear definitions of exposure and outcome </li></ul><ul><li>Use valid/reliable methods </li></ul><ul><li>Non-response can introduce bias </li></ul><ul><li>The primary concern in the design of any study must be validity </li></ul><ul><li>Large enough sample size </li></ul><ul><li>Do not over-interpret associations </li></ul>

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