Stats7.0

204 views
143 views

Published on

Published in: Technology, Economy & Finance
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
204
On SlideShare
0
From Embeds
0
Number of Embeds
3
Actions
Shares
0
Downloads
1
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Stats7.0

  1. 1. BASIC BIOSTATISTICS Diane Flynn, LTC, MC Colin Greene, LTC, MC
  2. 2. ObjectivesOverview of BiostatisticalTerms and ConceptsApplication of Statistical Tests
  3. 3. Why Use Statistics?Descriptive Statistics• identify patterns• leads to hypothesis generatingInferential Statistics• distinguish true differences from random variation• allows hypothesis testing
  4. 4. Why Use Statistics? Cardiovascular Mortality in Males 1.2 1 0.8SMR 0.6 Bangor 0.4 Roseto 0.2 0 35- 45- 55- 65- 75- 44 54 64 74 84 AJPH 1992
  5. 5. Types of DataNumerical • Continuous • DiscreteCategorical • Ordinal • Nominal
  6. 6. Descriptive StatisticsIdentifies patterns in the dataIdentifies outliersGuides choice of statistical test
  7. 7. Percentage of Specimens Testing Positive for RSV Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May JunSouth 2 2 5 7 20 30 15 20 15 8 4 3North- 2 3 5 3 12 28 22 28 22 20 10 9eastWest 2 2 3 3 5 8 25 27 25 22 15 12Mid- 2 2 3 2 4 12 12 12 10 19 15 8west
  8. 8. Descriptive Statistics Percentage of Specimens Testing Postive for RSV 1998-99353025 South20 Northeast15 West10 Midwest 5 0 Jul Sep Nov Jan Mar May Jul
  9. 9. Describing the Data with NumbersMeasures of Central Tendency • MEAN -- average • MEDIAN -- middle value • MODE -- most frequently observed value(s)
  10. 10. Distribution of Course Grades 14 12 10Number of 8 Students 6 4 2 0 A A- B+ B B- C+ C C- D+ D D- F Grade
  11. 11. Describing the Data with NumbersMeasures of Dispersion • RANGE • STANDARD DEVIATION • SKEWNESS
  12. 12. Measures of Dispersion• RANGE • highest to lowest values• STANDARD DEVIATION • how closely do values cluster around the mean value• SKEWNESS • refers to symmetry of curve
  13. 13. Measures of Dispersion• RANGE • highest to lowest values• STANDARD DEVIATION • how closely do values cluster around the mean value• SKEWNESS • refers to symmetry of curve
  14. 14. Standard DeviationCurve A Curve B σB σA
  15. 15. Measures of Dispersion• RANGE • highest to lowest values• STANDARD DEVIATION • how closely do values cluster around the mean value• SKEWNESS • refers to symmetry of curve
  16. 16. Skewness Curve A Curve BMode Median negative skew Mean
  17. 17. The Normal Distribution .Mean = median =mode Mean, Median, ModeSkew is zero68% of values fallbetween 1 SD95% of values fallbetween 2 SDs 1 2σ σ
  18. 18. Inferential StatisticsUsed to determine the likelihood that aconclusion based on data from asample is true
  19. 19. Termsp value: the probability that an observed difference could have occurred by chance
  20. 20. Hypertension TrialDRUG Baseline mean SBP F/u mean SBP A 150 130 B 150 125
  21. 21. Termsconfidence interval:The range of values we can be reasonably certain includes the true value.
  22. 22. 30 Day % MortalityStudy IC STK Control p NKhaja 5.0 10.0 0.55 40Anderson 4.2 15.4 0.19 50Kennedy 3.7 11.2 0.02 250
  23. 23. 95% Confidence Intervals Khaja (n=40)Anderson (n=50) Kennedy (n=250)-.40 -.35 -.30 -.25 -.20 -.15 -.10 -.05 .00 .05 .10 .15 .20
  24. 24. Types of Errors Truth No Difference differenceConclusion No TYPE II difference ERROR (β ) Difference TYPE I ERROR (α) Power = 1-β
  25. 25. What Test Do I Use?1. What type of data?2. How many samples?3. Are the data normally distributed?4. What is the sample size?

×