Using Computers for Data Analysis

1. Using Computers for Data Analysis Adam Schlichting University of Illinois at Chicago Department of Emergency Medicine

2. IntroductionWhy? • Too many calculations to do on a handheld calculator

3. IntroductionPrograms • EpiInfo • Centers for Disease Control and Prevention (CDC) • Free software • http://www.cdc.gov/epiinfo/

5. IntroductionPrograms • Statistical Program for Social Scientists (SPSS) • Easy to use, point and click • Similar to Microsoft Excel • Fairly powerful

7. IntroductionPrograms • Statistical Analysis Software (SAS) • Very powerful • Not so easy to use

9. IntroductionPrograms • Other Programs • PEPI • STATA • FOCUS

10. IntroductionPrograms • We’ll focus on: • SPSS • EpiInfo for special situations • Easiest to use • Tell you everything you need to know 99% of the time • Biostatisticians exist for the remaining 1%

11. SPSSThe Program

12. SPSSThe Program

13. SPSSImporting Data • Excel is easier to enter and manipulate data • Need to import data • Excel • Access • DBase • Delineated text • …

14. SPSSImporting Data: Specify File Type

15. SPSSImporting Data: Specify File Location

16. SPSSImporting Data: Import Variable Names

17. SPSSImported Data: Complete

18. SPSSSaving Imported Data as a SPSS File

19. SPSSSaving Imported Data as a SPSS File

20. SPSSAnalysis: Frequency Counts • Do frequency counts of everything • Points out errors that need to be cleaned • Look for obvious mistakes • Age = 650 instead of 65

21. SPSSAnalysis: Frequency Counts

22. SPSSAnalysis: Frequency Counts

23. SPSSAnalysis: Frequency Counts • Use shift/click and Ctrl/click to select variables

24. SPSSAnalysis: Frequency Counts

25. SPSSAnalysis: Frequency Counts

26. SPSSAnalysis: Frequency Counts

27. SPSSAnalysis: Frequency Counts: Printing

28. SPSSAnalysis: Frequency Counts: Printing

29. SPSSAnalysis: Central Tendency • Useful for demographics, lab values • Defaults: • N • Range • Mean • Standard Deviation

30. SPSSAnalysis: Central Tendency

31. SPSSAnalysis: Central Tendency • Use shift/click and Ctrl/click to select variables

32. SPSSAnalysis: Central Tendency

33. SPSSAnalysis: Central Tendency

34. SPSSAnalysis: Central Tendency

35. SPSSAnalysis: Crosstabs • Compare subgroups of catagorical variables on other variables • Not used for continuous variables • Our example: In this sample, does outcome differ by: prehospital GCS? sex?

36. SPSSAnalysis: Crosstabs

37. SPSSAnalysis: Crosstabs

38. SPSSAnalysis: Crosstabs

39. SPSSAnalysis: Crossabs

40. SPSSAnalysis: Crossabs

41. SPSSAnalysis: Crosstabs • Gives a nice breakdown of data • But how do we know if a relationship exists?

42. SPSSAnalysis: Crosstabs • Use Statcalc in EpiInfo to quickly calculate Odds Ratios, Relative Risks, Confidence Intervals and p-values

43. EpiInfoStatcalc

44. EpiInfoStatcalc

45. EpiInfoStatcalc

46. EpiInfoStatcalc • Must translate orientation in SPSS table into Exposure/disease orientation for Statcalc • Disease = outcome • Exposure = risk

47. EpiInfoStatcalc • Disease = outcome = Alive • 1 = alive, 28 days • 2 = dead, 28 days • Bad outcome (death) = + disease • Exposure = risk = sex • 1 = male • 2 = female

48. EpiInfoStatcalc

49. EpiInfoStatcalc Nothing significant

50. EpiInfoStatcalc • If we had other data…