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Analysis Of Medical Data

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    • 1. Analysis of Medical Data Research Perspective Nancy B. Clark. M.Ed. Director of Medical Informatics Education FSU College of Medicine Spring 2004 http://www.med.fsu.edu/informatics
    • 2. Objectives
      • Review statistical concepts to be on Step 1.
      • Determine what data exist relative to a clinical question or formal hypothesis
        • use IT to locate existing data sources
        • identify and locate existing data sets
          • Within institution
          • Outside institution
      • Analyze, interpret and report findings
        • Select and use appropriate computer software: Excel, SPSS
        • Use software to perform simple statistical analysis and portray results graphically
        • Interpret reports
    • 3. Prerequisite Skills (Step 1 USMLE)
      • Fundamental concepts of measurement
        • Scales of measurement
        • Distribution, central tendency, variability, probability
        • Disease prevalence and incidence
        • Disease outcomes (eg, fatality rates)
        • Associations (correlation or covariance)
        • Health impact (eg, risk differences and ratios)
        • Sensitivity, specificity, predictive values
    • 4. More Prerequisite Skills (Step 1 USMLE)
      • Fundamental concepts of hypothesis testing and statistical inference
        • Confidence intervals
        • Statistical significance and type I error
        • Statistical power and type II error  
    • 5. More Step 1 Topics
      • Fundamental concepts of study design
        • Types of experimental studies (eg, clinical trials, community intervention trials)
        • Types of observational studies (eg, cohort, case-control, cross-sectional, case series, community surveys)
        • Sampling and sample size
        • Subject selection and exposure allocation (eg, randomization, stratification, self- - selection, systematic assignment)
        • Outcome assessment
        • Internal and external validity
    • 6. Scales of Measure
      • Nominal – qualitative classification of equal value: gender, race, color, city
      • Ordinal - qualitative classification which can be rank ordered: socioeconomic status of families
      • Interval - Numerical or quantitative data: can be rank ordered and sizes compared : temperature
      • Ratio - interval data with absolute zero value: time or space
    • 7. Distribution, Central Tendency… Mean
    • 8. …Variability, Probability…
      • Mean
      • Median
      • Mode
      • Standard deviation
      • Statistical Significance p < .01
    • 9. Confidence Interval
    • 10. Statistical Significance Type I and Type II errors Null Hypothesis = H o Type II error Correct decision Do Not Reject H o Correct decision Type I error Reject H o H o False H o True
    • 11. Statistics Online Textbook
      • The Statistics Homepage
      • http://www.statsoftinc.com/textbook/stathome.html
    • 12. Disease Prevalence and Incidence
      • Prevalence
        • probability of disease in entire population at any point in time
        • 2% of the population has diabetes
      • Incidence
        • probability that patient without disease develops disease during interval
        • 0.2% or 2 per 1000 new cases per year
    • 13. Sensitivity, Specificity
      • sensitivity = a / (a+c)
      • specificity = d / (b+d)
      d c Test is negative b a Test is positive Patients without disease Patients with disease
    • 14. Predictive Value
      • Positive predictive value = a / ( a+b)
      • Negative predictive value = d / (c+d)
      • Post-test probability of disease given positive test = a / (a+b)
      • Post-test probability of disease given negative test = c / (c+d)
      d c Test is negative b a Test is positive Patients without disease Patients with disease
    • 15. Good Resource Sen, Spc, PV
      • An Introduction to Information Mastery
      • http://www.poems.msu.edu/InfoMastery/default.htm
        • Diagnosis
          • Sensitivity and specificity
          • Predictive values
          • Likelihood ratios
      • InfoRetriever
        • Calculators: Epidemiology, Diagnostic test
    • 16. Fundamental Concepts of Study Design
      • Good Resource
        • Epidemiology for the Uninitiated
        • BMJ
        • Online Textbook
        • http://bmj.com/collections/epidem/epid.shtml
    • 17. Finding Health Statistics
    • 18. Types of Health Statistics Questions
      • Fact lookups
      • Research
      • Presentations
      • Social and Policy indicators
    • 19. Strategies for Finding Health Stats
      • Use Portal
      • Start at Internet site
      • Start with book or article
    • 20. Internet Portals of Health Stats
      • Lists of links that provide starting points for browsing or searching
        • Keyword search in portal vs Google
        • General idea what you want
      • The Related Health Services Research Web Sites http://www.nlm.nih.gov/nichsr/hsrsites.html
      • The NCHS portal: http://www.cdc.gov/nchs/
    • 21. Other Statistical Web Sites
      • CDC Data and Statistics http://www.cdc.gov/scientific.htm
      • FedStats Home Page http://www.fedstats.gov/
      • Compare these two
      • U Michigan’s Statistical Resources on the WEB – HEALTH
      • What type of stats
    • 22. Lexis-Nexis Statistical Universe
      • Subscription resource
      • Searches stat data
        • Subject List
        • Limit search
        • Reports or tables
      • http://web.lexis-nexis.com/statuniv?B1=Connect+to+Statistical+Universe
    • 23. MMWR
      • Morbidity – illness
      • Mortality – death
      • http://www.cdc.gov/mmwr/
      • Disease Trends
      • Tables - searchable
    • 24. Health Care Data
      • Healthcare Cost and Utilization Project
      • HCUPnet
      • Hospital discharges
      • Ambulatory service
      • Costs
      • Amount of care
      • By diagnosis and procedure
      • Surveys of hosp, physicians, nursing homes
    • 25. Health Consequences
      • Costs to society, individuals
      • Cost from care
      • Costs of illness
      • Impact on infrastructure
      • HCFA=>CMS Health Accounts
      • http://www.cms.hhs.gov/statistics/nhe/default.asp
    • 26. State and International Data
      • Floridahealthstat.com - Where Florida Health Data Resides
      • DOH Epidemiology
      • KFF State Health Facts Online
      • United Nations Statistics Division
      • World Health Organization Research Tools
    • 27. Individual Datasets
      • EMR
      • Billing
      • CDCS
      • Customized data collection tools
    • 28. Data Analysis
    • 29. Selecting the Appropriate Software
      • Spreadsheet
        • Numerical (interval or ratio) data
        • Sums
        • Averages
        • Standard deviations
        • Simple charts and graphs
      • Statistical Software
        • Nominal or Ordinal data
        • Comparisons of two+ groups
        • Frequency tables
        • Complicated charts and graphs
        • Normal curves
        • Class intervals
        • Statistical significance
    • 30. Spreadsheets
      • Excel
      • Pocket Excel
    • 31. Data Tables
      • Field names at top
      • Each row is a record (sample)
      • Sorting whole table
        • By one column
        • By more than one column
      • Sorting individual sections
    • 32. Descriptive Statistics
      • Distribution
        • frequency distribution
        • Histogram
      • Central tendency
        • Mean
        • Median
        • mode
      • Dispersion
        • Range
        • Standard deviation
        • Variance
      • N
      • Not P (inferential stats)
    • 33. Central Tendency
      • Mean
        • =AVERAGE(b2:b1500)
      • Median
        • =MEDIAN(A2:A7)
      • Mode
        • =MODE(A2:A7)
      • N
        • =COUNT(A2:A1500)
        • =COUNTBLANK(A2:B5)
    • 34. Dispersion
      • Range
        • =MAX(A2:A60)- MIN(A2:A60)
      • Standard deviation
        • =STDEV(A2:A110)
      • Variance
        • =VAR(A2:A110)
    • 35. Distribution
      • Frequency distribution
        • Not easy – use SPSS
        • FREQUENCY(data_array,bins_array)
        • Use help
      • Histogram
        • Bar chart of frequency table
    • 36. Hands on experience
      • Analyze data in examples2.xls
    • 37. Statistical Software Intro to SPSS
    • 38. Statistical Software
      • SPSS
      • Provided by request/justification
      • Lab Computers
      • Start => Programs => SPSS for Windows => SPSS 11.0 for Windows
    • 39. Start Screen
      • Don’t show this dialog in the future.
      • OK
    • 40. Open Breast Cancer Survival Data View
    • 41. Views Variables View
    • 42. File Information
      • Utilities Menu
      • File Info…
      • Output window
    • 43. Descriptive Statistics
      • Analyze Menu
      • Descriptive Statistics
      • Frequencies
      • Select Age ►
      • Click Statistic s button
      • In Central Tendency
        • Mean, Median, Mode
      • In Dispersion
        • Standard Deviation, variance
      • In Percentile Values
        • Quartiles
      • Continue
      • OK
    • 44. Graphing
      • Graphs Menu
        • Pie…
      • Summary for Groups of cases
      • Lymph Nodes ►
      • OK
    • 45. Histogram with Normal Curve
      • Graphs Menu
        • Histogram..
      • Select Age ►
      • Check Display Normal Curve
      • OK
    • 46. Simple Correlation Analysis
      • Age and Tumor Size
      • Analyze Menu
        • Correlate…
          • Bivariate
      • Select Age ►
      • Select Pathological Tumor Size ►
      • Check Pearson and Spearman – Two tailed
      • OK
      • Is there a correlation? Negative or Positive?
      • Is it statistically significant?
    • 47. Save Output
      • Save on All Users drive
      • Under Nancy.clark
      • SPSS Output Files
      • Name it your name: ie, KerryBachista.spo
    • 48. Importing Data
      • From Excel, SAS, dBase, etc.
      • Variable names first row
      • File Menu, Open
        • Data…
      • Files of Type
        • Excel
      • Tutorial, Samples
        • Demo.exe
      • Type in Labels
      • Pick Type of variable
      • Enter Value Labels
      • Etc.
    • 49. SPSS Tutorials
      • In the Help Menu
      • On Informatics Web page
      • Books:
        • Statistics for Social & Health Research (Sage)
          • Argyrous, George
        • Statistics Applied to Clinical Trials (Klawer Academic Publishers)
          • Cleophas, Ton J., et al
    • 50. Objectives
      • Determine what data exist relative to a clinical question or formal hypothesis
        • use IT to locate existing data sources
        • identify and locate existing data sets
          • Within institution
          • Outside institution
      • Analyze, interpret and report findings
        • Select appropriate computer software: Excel, SPSS
        • Use software to perform simple statistical analysis and portray results graphically
        • Interpret reports
    • 51. Questions?