Role of statistics in biomedical research


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Role of statistics in biomedical research

  1. 1. Role of statistics in biomedical research Name:eman raouf ahmed youssif Medical research institute
  2. 2. The content:
  3. 3. introduction
  4. 4. introduction Statistics is the science that deals with data Collection of data Presentation of data Analysis of data
  5. 5. 1-collection of data Data could either be Constant variable
  6. 6. Variables types of data are divided in to : Continuous discrete nominal ordinal quantitative qualitative
  7. 7. 2-presentation of data 1-the average *mean *median *mode *the mid range *the proportion The percent
  8. 8. Continue presentation of data 2- measure of dispersion *the standard deviation *the minimum and maximum *the range
  9. 9. Statistics-example Comment The median age of the sample is 6 years old ranging from 1-18 years old. The mean hemoglobin is 7.7+- 3.1 gm/dl Hbage 7.77.65mean 6.96median 3.094.8Std. deviation 31minimum 1418maximum
  10. 10. Graphical presentation of data 1-presentation of the distribution of a qualitative variable and quantitative discrete 1- bar chart 2-the pie chart
  11. 11. 2- presentation of the distribution of a quantitative continuous variable 1-the histogram 2-the frequency polygon 3-The frequency curve
  12. 12. 3-presentation of a quantitative variable The box plot The error bar
  13. 13. Hypothesis testing and statistical significance
  14. 14. 3-Analysis of data
  15. 15. Epidemiological studies 1-descriptive epidemiological studies Types: Case report Case series report Correlational studies Cross sectional studies 2-Analytical epidemiological studies Case control studies Cohort studies A-prospective cohort B-retrospective cohort 3-Research designs Experimental designs Clinical trials Meta analysis
  16. 16. 1- descriptive epidemiological studies A- case report B-case series report: Utilities of case report and case series report *identify a new case Formulate a new hypothesis Limitations of case report and case series *the case report is based on the experience of only person so the presence of any exposure may be coincidental •The lack of of the comparison group in case series report can’t prove an association •So both of them can’t be used to test the presence or absence of association
  17. 17. Continue descriptive C-correlational study Example: 1-disease frequencies between different populations during the same period of time E.g.: correlation between the average daily consumption of meat and the rate of cancer colon in women from different countries So countries with lower average meat intakes have the lowest rates of cancer colon and vice versa 2-disease frequencies in the same population at different population at different points of time. e.g. observation of the deaths from coronary heart diseases during the years from 1968 to 1977 revealed gradual decline and it was lower than the expected values.
  18. 18. Continue descriptive –correlation study Advantages: Quick and inexpensive They generate hypothesis Limitations: They can’t be used for testing the hypothesis (never prove causation) It’s impossible to link exposure and disease in particular individual
  19. 19. Continue descriptive- cross sectional study (prevalence studies) Incidence and prevalence
  20. 20. Continue cross sectional study: Benefits of cross sectional study: It shows the association between exposure and disease It’s quick and cheap It’s suitable for relatively frequent disease with long latency Generate hypothesis Limitations of cross sectional study *data deals with survival (who died or cured) are not included *it can’t be used in acute diseases of short duration It’s not suitable for rare diseases Can’t test hypothesis
  21. 21. Analytical epidemiological studies *case –control studies *cohort studies A-prospective cohort B-retrospective cohort C-clinical trial
  22. 22. A-case-control study Steps: 1- selection of cases 2-selection of control 3-assesment of exposure 4-analysis and interpretation of the results
  23. 23. The main advantage of the case-control study *easy, rapid and cheap *require few subjects *suitable for rare diseases *suitable for diseases with long latency period *examine multiple etiologic factors for a single disease. *estimation of the risk allow us to test a hypothesis, so preventive program can be established *no follow up of cases so no attrition bias
  24. 24. Limitations of the case –control study
  25. 25. Cohort study-prospective cohort Steps: *selection of the cohort *obtaining data on exposure *follow up *analysis and interpretation of the results
  26. 26. Clinical trials(types and phases)
  27. 27. references
  28. 28. THANK YOU