33861 - Introduction to Biostatistics

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33861 - Introduction to Biostatistics

  1. 1. ‫الرحيم‬ ‫الرحمن‬ ‫ال‬ ‫بسم‬‫الرحيم‬ ‫الرحمن‬ ‫ال‬ ‫بسم‬
  2. 2. Introduction toIntroduction to BiostatisticsBiostatistics Dr. Moataza Mahmoud Abdel Wahab Lecturer of Biostatistics High Institute of Public Health University of Alexandria
  3. 3. BiostatisticsBiostatistics (a portmanteau word made from biology and statistics) The application of statistics to a wide range of topics in biology.
  4. 4. BiostatisticsBiostatistics It is the science which deals with development and application of the most appropriate methods for the: Collection of data. Presentation of the collected data. Analysis and interpretation of the results. Making decisions on the basis of such analysis
  5. 5. Other definitions for “Statistics”  Frequently used in referral to recorded data  Denotes characteristics calculated for a set of data : sample mean
  6. 6. Role of statisticians  To guide the design of an experiment or survey prior to data collection  To analyze data using proper statistical procedures and techniques  To present and interpret the results to researchers and other decision makers
  7. 7. Sources of data Records Surveys Experiments Comprehensive Sample
  8. 8. Types of dataTypes of data Constan t Variable s
  9. 9. Quantitative continuous Types of variables Quantitative variables Qualitative variables Quantitative descrete Qualitative nominal Qualitative ordinal
  10. 10.  Numerical presentationNumerical presentation  Graphical presentationGraphical presentation  Mathematical presentationMathematical presentation Methods of presentation of data
  11. 11. 1- Numerical presentation Tabular presentation (simple – complex) Simple frequency distribution Table (S.F.D.T.) Title Name of variableName of variable (Units of variable)(Units of variable) FrequencyFrequency %% -- - Categories- Categories -- TotalTotal
  12. 12. Table (I): Distribution of 50 patients at the surgical department of Alexandria hospital in May 2008 according to their ABO blood groups BloodBlood groupgroup FrequencyFrequency %% AA BB ABAB OO 1212 1818 55 1515 2424 3636 1010 3030 TotalTotal 5050 100100
  13. 13. Table (II): Distribution of 50 patients at the surgical department of Alexandria hospital in May 2008 according to their age AgeAge (years)(years) FrequencyFrequency %% 20-<3020-<30 30-30- 40-40- 50+50+ 1212 1818 55 1515 2424 3636 1010 3030 TotalTotal 5050 100100
  14. 14. Complex frequency distribution Table Table (III): Distribution of 20 lung cancer patients at the chest department of Alexandria hospital and 40 controls in May 2008 according to smoking Smoking Lung cancer Total Cases Control No. % No. % No. % Smoker 15 75% 8 20% 23 38.33 Non smoker 5 25% 32 80% 37 61.67 Total 20 100 40 100 60 100
  15. 15. Complex frequency distribution Table Table (IV): Distribution of 60 patients at the chest department of Alexandria hospital in May 2008 according to smoking & lung cancer Smoking Lung cancer Total positive negative No. % No. % No. % Smoker 15 65.2 8 34.8 23 100 Non smoker 5 13.5 32 86.5 37 100 Total 20 33.3 40 66.7 60 100
  16. 16. 2- Graphical presentation  Graphs drawn using Cartesian coordinates • Line graph • Frequency polygon • Frequency curve • Histogram • Bar graph • Scatter plot  Pie chart  Statistical maps rules
  17. 17. Line Graph 0 10 20 30 40 50 60 1960 1970 1980 1990 2000 Year MMR/1000 Year MMR 1960 50 1970 45 1980 26 1990 15 2000 12 Figure (1): Maternal mortality rate of (country), 1960-2000
  18. 18. Frequency polygon Age (years) Sex Mid-point of intervalMales Female s 20 - 3 (12%) 2 (10%) (20+30) / 2 = 25 30 - 9 (36%) 6 (30%) (30+40) / 2 = 35 40- 7 (8%) 5 (25%) (40+50) / 2 = 45 50 - 4 (16%) 3 (15%) (50+60) / 2 = 55 60 - 70 2 (8%) 4 (20%) (60+70) / 2 = 65 Total 25(100%) 20(100%)
  19. 19. Frequency polygon Age Sex M-P M F 20- (12%) (10%) 25 30- (36%) (30%) 35 40- (8%) (25%) 45 50- (16%) (15%) 55 60-70 (8%) (20%) 65 0 5 10 15 20 25 30 35 40 25 35 45 55 65 Age % Males Females Figure (2): Distribution of 45 patients at (place) , in (time) by age and sex
  20. 20. 0 1 2 3 4 5 6 7 8 9 20- 30- 40- 50- 60-69 Age in years Frequency Female Male Frequency curve
  21. 21. HistogramHistogram 0 5 10 15 20 25 30 35 0 25 30 40 45 60 65 Age (years) % Figure (2): Distribution of 100 cholera patients at (place) , in (time) by age
  22. 22. Bar chart 0 5 10 15 20 25 30 35 40 45 % Single Married Divorced Widowed Marital status
  23. 23. Bar chart 0 10 20 30 40 50 % Single Married Divorced Widowed Marital status Male Female
  24. 24. Pie chart Deletion 3% Inversion 18% Translocation 79%
  25. 25. Doughnut chart Hospital A Hospital B DM IHD Renal
  26. 26. 3-Mathematical presentation Summery statistics Measures of locationMeasures of location 1- Measures of central tendency1- Measures of central tendency 2- Measures of non central locations2- Measures of non central locations (Quartiles, Percentiles )(Quartiles, Percentiles ) Measures of dispersionMeasures of dispersion
  27. 27. 1- Measures of central tendency (averages) MidrangeMidrange Smallest observation + Largest observationSmallest observation + Largest observation 22 ModeMode the value which occurs with the greatestthe value which occurs with the greatest frequencyfrequency i.e.i.e. the most common valuethe most common value Summery statistics
  28. 28. 1- Measures of central tendency (cont.)  MedianMedian the observation which lies in the middle ofthe observation which lies in the middle of the ordered observation.the ordered observation.  Arithmetic mean (mean)Arithmetic mean (mean) Sum of all observationsSum of all observations Number of observationsNumber of observations Summery statistics
  29. 29. Measures of dispersion  RangeRange  VarianceVariance  Standard deviationStandard deviation  Semi-interquartile rangeSemi-interquartile range  Coefficient of variationCoefficient of variation  ““Standard error”Standard error”
  30. 30. Standard deviation SD 7 7 7 7 7 7 7 8 7 7 7 6 3 2 7 8 13 9Mean = 7 SD=0 Mean = 7 SD=0.63 Mean = 7 SD=4.04
  31. 31. Standard error of mean SE A measure of variability among means of samples selected from certain population SE (Mean) =SE (Mean) = SS nn

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