Introduction to biostatistics
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Introduction to biostatistics

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Introduction to biostatistics lecture by Prof. Faisal Farahat, as part of the 5th Research Summer School - Jeddah held by KAIMRC - WR

Introduction to biostatistics lecture by Prof. Faisal Farahat, as part of the 5th Research Summer School - Jeddah held by KAIMRC - WR

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  • 1. 1June 22, 2013 Dr Fayssal Farahat, MD 1Dr. Fayssal M Farahat,MBBCh, MSc, PhDConsultant Public HealthInfection Prevention and ControlKing AbdulAziz Medical City–JeddahNational Guard Health AffairsDescriptive StatisticsJune 22, 2013 Dr Fayssal Farahat, MD 2“Whatever you can notmeasure, you can notmanage”June 22, 2013 Dr Fayssal Farahat, MD 3Statisticsbusiness education psychologyBiology and MedicineBiostatistics
  • 2. 2June 22, 2013 Dr Fayssal Farahat, MD 4StatisticsCollection Presentation AnalysisDraw inferencesJune 22, 2013 Dr Fayssal Farahat, MD 5Data = numbersMeasurement CountingA nurse takes apatient’stemperatureA hospitaladministrator countsnumber of dischargedpatients on a givenday.June 22, 2013 Dr Fayssal Farahat, MD 6DataDataDataDataDecisionThe procedure bywhich we reach aconclusion about apopulation on thebasis of informationcontained in a sampledrawn from thispopulation
  • 3. 3June 22, 2013 Dr Fayssal Farahat, MD 7Students’ scores:75, 95, 60, 93, 85, 84, 76, 92, 62, 83,80, 90, 64, 75,79, 32, 78, 64, 98,73,88, 61, 82, 86, 79, 78, 80, 55How useful would that list of number be to you?How to get information out of data …FIRST STEP, the data have to be organized and Summarized.Data INFOJune 22, 2013 Dr Fayssal Farahat, MD 8Sources of DataPrimary DataCollection & AnalysisSecondary DataCollection & AnalysisClient satisfaction & Identification SurveysLifestyle and health behavior surveysFocus Group discussionsHospital Recordsinpatients outpatients Birth DeathExternal sources (published reports)June 22, 2013 Dr Fayssal Farahat, MD 9Measurement
  • 4. 4June 22, 2013 Dr Fayssal Farahat, MD 10Variable=Characteristicnot the same when observed in different possessors.June 22, 2013 Dr Fayssal Farahat, MD 11VARIABLESJune 22, 2013 Dr Fayssal Farahat, MD 12QuantitativeDiscrete‫منفصلة‬No fractions‫عشرية‬ ‫كسور‬ ‫ال‬Continuous‫متصلة‬Fractions‫عشرية‬ ‫كسور‬
  • 5. 5June 22, 2013 Dr Fayssal Farahat, MD 13QualitativeOrdinal‫ترتيبية‬Nominal‫اسمية‬June 22, 2013 Dr Fayssal Farahat, MD 14Discrete‫منفصلة‬• Number of pregnancies• Number of children• Family size• Heart rate• Respiratory rate• Number of cigarettesJune 22, 2013 Dr Fayssal Farahat, MD 15Continuous‫متصلة‬• WEIGHT• HIGHT• AGE• TEPERATURE• BLOOD PRESSURE• RBS• AMOUNT OF URINE• BODY SURFACE AREA
  • 6. 6June 22, 2013 Dr Fayssal Farahat, MD 16Nominal- Gender :" Male – female. "- Marital status: married, single, widow, divorced(1) (2)(1) (2) (3) (4)June 22, 2013 Dr Fayssal Farahat, MD 17Ordinal- grade :" A+ A B+ B C+ C D+ D ".- Educational level: 1ry, 2ry, university- Income: < 5000, 5000-10.000, >10.000(1) (2) (3) (4) (5) (6) (7)(1) (2) (3)(1) (2) (3)June 22, 2013 Dr Fayssal Farahat, MD 18Quantitative QualitativeHigh systoleQualitativexQuantitative200x
  • 7. 7June 22, 2013 Dr Fayssal Farahat, MD 19Measurement ScalesNominalOrdinalIntervalRatioJune 22, 2013 Dr Fayssal Farahat, MD 20TemperatureTruezeroWeightJune 22, 2013 Dr Fayssal Farahat, MD 21The distinction is not aboutthe value, but the association,causality each variableoccupies in the equation.
  • 8. 8June 22, 2013 Dr Fayssal Farahat, MD 22Frequency table‫التكراري‬ ‫الجدول‬Interval‫الفترة‬Frequency‫التكرار‬Valid %‫المئوية‬ ‫النسبة‬Cumulative %‫التراكمية‬ ‫النسبة‬<2020-2930-3940-4950-5960-6970-7980-89≥90Total467010810674724229335807.912.118.618.312.812.47.25.05.7100.07.920.038.656.969.782.189.394.3100Few6-14Overlap40-49, 49-50Equal widthAvoidopen-endedCumulative %=Obs % + all lower %<60June 22, 2013 Dr Fayssal Farahat, MD 23CityMale smokers ‫المدخنون‬TaifRiyadhJeddahTOTALTable (1). Number and percent of male smokersless and more than 18 ys old in different cities< 18 years > 18 yearsn % n %8090150320TOTALn %4030303212021035068060707068200 1003005001000100100100TablesJune 22, 2013 Dr Fayssal Farahat, MD 24TablesCityMale smokersTaifRiyadhJeddahTOTALTable (1). Number and percent of male smokersless and more than 18 ys old in different cities< 18 years > 18 yearsn % n %8090150320TOTALn %252847100120210350680183151100200 2030050010003050100
  • 9. 9June 22, 2013 Dr Fayssal Farahat, MD 252 x 2ExposureSmokerNon-smokerCancer LungPositiveN (%)NegativeN (%)June 22, 2013 Dr Fayssal Farahat, MD 26GraphsLine graphFrequency HistogramFrequency polygonBar chartPie chartPictogramJune 22, 2013 Dr Fayssal Farahat, MD 27TimePositiveNo relationNegativeVariableXY+-0
  • 10. 10June 22, 2013 Dr Fayssal Farahat, MD 28XYEqual widthJune 22, 2013 Dr Fayssal Farahat, MD 29Frequency Polygone‫التكراري‬ ‫المنحنى‬June 22, 2013 Dr Fayssal Farahat, MD 30 heal thy diseasegroup246810CountHealthy DiseasedCount
  • 11. 11June 22, 2013 Dr Fayssal Farahat, MD 3139.758.8gp 1gp 2AgeJune 22, 2013 Dr Fayssal Farahat, MD 32Sex distribution in different studied groups01020304050607080Control Asthmatic COPD%MaleFemaleJune 22, 2013 Dr Fayssal Farahat, MD 33healthydiseasegroupPies show countsPie44.44%8.055.56%10.0Pie Chart
  • 12. 12June 22, 2013 Dr Fayssal Farahat, MD 34Pictogram1970 1980 1990 2000June 22, 2013 Dr Fayssal Farahat, MD 3502468101214Y1950 Y1960 Y1970 Y1980 Y1990 Y2000YearMortality(per1000)2468101214012341970y 1980y 1990y 2000yJune 22, 2013 Dr Fayssal Farahat, MD 36Summarizing qualitative dataProportiona / a + b (part / whole)PercentageProportion X 100%Ratioa / b (part / another part)Ratea / a + b X base (1000, 10,000,100,000)+ In a specific time (20 per 10,000 per year)
  • 13. 13June 22, 2013 Dr Fayssal Farahat, MD 37Arithmetic MeanExtremesHRvariation1234567891019.251.933.186.729.145.316.485.718.942.642.932.1Consider each variableXJune 22, 2013 Dr Fayssal Farahat, MD 38Weighted MeanInterval Frequency Valid % Cumulative %2-2021-3031-4041-5051-6061-7071-8081-90>90Total467010810674724229335807.912.118.618.312.812.47.25.05.7100.07.920.038.656.969.782.189.394.3100[(11 x 46) + (25 x 70) + ….+ (85 x 29) + (100 x 33)] / 580 = 49.1X?June 22, 2013 Dr Fayssal Farahat, MD 39MedianMiddle observationOdd EvenExtremesConsider each variableOrdinal data
  • 14. 14June 22, 2013 Dr Fayssal Farahat, MD 40ModeMost frequent valueUni-modal Bi-modalMost frequent intervalMost frequent diagnosisJune 22, 2013 Dr Fayssal Farahat, MD 41Measures of Spread‫التشتت‬ ‫مقاييس‬RangeSDCVPercentilesInterquartileRange‫المدى‬‫المعياري‬ ‫االنحراف‬‫التغير‬ ‫معامل‬Percentiles‫الربعي‬ ‫المدى‬June 22, 2013 Dr Fayssal Farahat, MD 42The RangeThe largest – the smallest
  • 15. 15June 22, 2013 Dr Fayssal Farahat, MD 43June 22, 2013 Dr Fayssal Farahat, MD 44Coefficient of Variation‫التغير‬ ‫معامل‬Measure 1 70 (31)Measure 2105 (48)CanweCompare2 different scales2 different investigatorsCV = (SD / Mean) x 10044.3 % 45.7 %QualityControlJune 22, 2013 Dr Fayssal Farahat, MD 45
  • 16. 16June 22, 2013 Dr Fayssal Farahat, MD 46Interquartile Range‫الربعي‬ ‫المدى‬= the difference between the 25th and 75th percentiles25th 75thCentral 50%6.5 kg 7.5 kg1st 3rdJune 22, 2013 Dr Fayssal Farahat, MD 47STEM‫الساق‬LEAF‫الورقة‬234565689001136902690302730.0033.0031.0029.0030.0031.0026.0028.0036.0039.0040.0049.0050.0060.0067.0046.0042.0025.0062.0053.00Stem and Leaf PlotJune 22, 2013 Dr Fayssal Farahat, MD 48Box – and whisker plot
  • 17. 17June 22, 2013 Dr Fayssal Farahat, MD 49Normal Distribution CurveGaussian Distribution CurveJune 22, 2013 Dr Fayssal Farahat, MD 50MeanMedianModeBell Shape68%SymmetricJune 22, 2013 Dr Fayssal Farahat, MD 51MeanMedianModeBell Shape95%Symmetric
  • 18. 18Normal curves(μ=0, σ2=1) and (μ=5, σ 2=1)-2 0 2 4 6 8x0.00.10.20.30.4fx1Normal curves(μ=0, σ2=1) and (μ=0, σ2=2)-3 -2 -1 0 1 2 3x0.00.10.20.30.4yNormal curves(μ=0, σ2=1) and (μ=2, σ2=0.25)-2 0 2 4 6 8x0.00.20.40.60.81.0fx1
  • 19. 19June 22, 2013 Dr Fayssal Farahat, MD 558 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0 1 5 0 1 6 0051 01 52 02 5PercentP O U N D S120 13011068% of 100 = .68 x 100 = ~ 68 students8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0 1 5 0 1 6 0051 01 52 02 5PercentP O U N D S12010095% of 100 = .95 x 120 = ~ 95 students140130110
  • 20. 208 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0 1 5 0 1 6 0051 01 52 02 5PercentP O U N D S120100 1401301100 +1 +2-1-2XZ130 – 12010x – μσ8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0 1 5 0 1 6 0051 01 52 02 5PercentP O U N D S120100 1401301101260 +1 +2-1-2x – μσLooking up probabilities in thestandard normal tableZ=0.60Z=0.00
  • 21. 21What is the area to theleft of Z=1.51 in astandard normal curve?Z=1.51Z=1.51Area is93.45%