医学统计学ppt英文课件CHO2descriptionofmeasurementdata

DescriptionofMeasurementData Chapter2 Content FrequencydistributionDescriptionsofcentraltendencyMeasuresofdispersionNormaldistributionRangeofreferencevalue Section1FrequencyDistribution 1 Frequencytable Example2 1Toacquirethevaluesoftotalcholesterolinserumof101healthyfemaleadultsasbelow andtoworkoutthefrequencytable Approach 1 Range Thedifferencebetweenthemaximumandtheminimum R 2 ClassInterval i Usuallydividedinto10 15groups 3 Group Lowerlimit L thebeginningofeverygroupUpperlimit U theendofeverygroup Group2 30 2 60 2 90 3 20 5 60 5 90 2 30 2 60 4 GroupingandCountingFrequencies 2 30 2 60 2 Graphoffrequencydistribution 3 Useoffrequencytableandgraphoffrequencydistribution 1 Describingthetypeoffrequenciesdistribution 1 Symmetricdistribution 2 Skewedtotherightdistribution Positivelyskeweddistribution 3 Skewedtotheleftdistribution negativelyskeweddistribution 2 Describingthecharacteristicoffrequenciesdistribution3 Findingshadinessvalue4 Convenientfornextstatisticalanalysisandmanagement Section2DescriptionsofCentralTendency Averageincommonuse MeanGeometricmeanMedian 1 Mean Adescriptivestatisticusedasameasureofcentraltendency Allscoresinasetofscoresareaddedtogetheranddividedbythenumberofsubjects 1 CalculateMethod DirectAccount Formula Example2 2Tocalculatemeanofthevaluesoftotalcholesterolinserumof100healthyfemaleadultsindirectmethod WeightingMethod Formula Example2 3Calculatethemeanofvaluesintable2 1byweightingmethod 2 Application AdapttodescribeSymmetricdistribution speciallyofnormaldistributiondata 2 Geometricmean Thegeometricmeanissimplytheaverageofsymmetricvaluesafterlogarithmtransition 1 CalculateMethodDirectmethodFormula or Example2 4Toacquirereciprocaltiterofseraasbelow calculatethegeometricmean 10 20 40 40 160 Weightingmethod Formula 2 Application Adapttodataofgeometricprogressiongrowth especiallyoflogarithmnormaldistribution 3 MedianandPercentile 1 MedianThemedianisthescore valuethatisexactlyinthemiddleofadistribution Formula n oddnumbern evennumber Example2 5Calculatethemediumoflatentperiodof7patientsasbelow 2 3 4 5 6 9 16 Example2 6Calculatethemediumoflatentperiodof8patientsasbelow 1 2 2 3 5 8 15 24 Application 1 Allkindsofdata2 Dataofskeweddistributionandthoseofnoexactvalueinoneendortwo 2 Percentile Percentileisakindofpositionindex Directmethod decimalfraction integer Example2 7Calculateno 5andno 99percentileasbelow Patients Daysinhospital n 120 120X5 6 Weightingmethod Formula Section3MeasuresofDispersion RangeQuartileVarianceandStandardDeviationCoefficientofVariation 1 RangeThedifferencebetweenthemaximumandtheminimum R 2 Quartile QR LowerQuartileUpperQuartile 3 VarianceandStandardDeviation Variance Ameasureofdispersionorvariability spread calculatedbysquaringthevalueofthestandarddeviation Samplevariance PopulationstandarddeviationSamplestandarddeviation Samplestandarddeviationcanalsobecalculatedasbelow Example2 8Calculatethestandarddeviationofvaluesintable2 1 4 CoefficientofVariation Unit4NormalDistribution Fig 2 3 FrequenciesDistributionApproachestiNormalDistribution 1 Concept Mathematicfunctionexpression 2 Characteristic BellCurveThenormalcurvewasdevelopedmathematicallyin1733 Gaussusedthenormalcurvetoanalyzeastronomicaldatain1809 ThenormalcurveisoftencalledtheGaussiandistribution Thetermbell shapedcurveisoftenusedineverydayusage TwoParametersThenormaldistributionischaracterizedbytwoparameters themean andthestandarddeviationsigma Themeanisameasureoflocationorcenterandthestandarddeviationisameasureofscaleorspread Themeancanbeanyvaluebetweeninfinityandthestandarddeviationmustbepositive Eachpossiblevalueof andsigmadefineaspecificnormaldistributionandcollectivelyallpossiblenormaldistributionsdefinethenormalfamily Fig 2 4PositionTransformofNormalDistribution Fig 2 5Illustrationforthechangingofnormaldistribution DistributioncharacteristicsofProportion Fig 2 6 ProportionRuleofNormalDistribution 3 StandardNormalDistribution Thestandard orcanonical normaldistributionisaspecialmemberofthenormalfamilythathasameanof0andastandarddeviationof1 Thestandardnormaldistributionisimportantsincetheprobabilitiesandpercentilesofanynormaldistributioncanbecomputedfromthestandardnormaldistribution if andsigmaareknown Unit5MedicalReferenceRange 1 ConceptThereferencerangeisderivedmathematicallybytakingtheaveragevalueforthemassnormalpopulationandallowingfornaturalvariationaroundthatvalue One sided Two sidedMedicalreferencerangeinclude Andisincommonuse 2 CalculateMedicalReferenceRange 1 NormalDistributionMethod2 PercentileMethod Formula NormalDist