1 STAT 6020 Introduction to Biostatistics Fall 2005 Dr. G. H. Rowell Class 3.
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1 STAT 6020 Introduction to Biostatistics Fall 2005 Dr. G. H. Rowell Class 3
2 Ch 5: REVIEW from your Homework Students in the class will take turns defining the terms listed in this presentation that they have listed in their homework. Examples are helpful if you have them included, please mention them.
3 Ch5: Designing Research, Overview: Observational Study REVIEW
5 Ch 5: Some Definitions Observational Study vs. Experiment Prospective vs. Retrospective Longitudinal vs. Cross-sectional Control vs. Treatment REVIEW
6 Ch 5: Sources of Variation Variation: control what you can, randomize what you cannot control Cautions: Samples need to represent the population In comparative studies, make groups similar with respect to known sources of variation
7 Planning a Good Experiment, 2 (Cobb, Introduction to Experimental Design, Springer, 1998.) The Content of an Experiment: 3 Decisions to Make
8 Planning a Good Experiment, 1 (Cobb, Introduction to Experimental Design, Springer, 1998.) Three SOURCES of Variability: One We Want and Two We Don’t Want
9 Planning a Good Experiment, 1 (Cobb, Introduction to Experimental Design, Springer, 1998.) Three KINDS of Variability: One We Want, One We Can Live With, and One That Threatens Disaster
12 Ch 5L Experiment Structure See diagrams on Pages 83 – 85
13 Ch 5.7: Random Allocation For Hand-in Homework: Name: Randomization Simulation Due Date: Monday, Sept. 19 at 9:30 AM CST Possible Points: 20 Complete the Randomization Simulation Activity found at http://mtsu.edu/~smcdanie/I_cubed/Lesson2/lesson2- Home.htm Be sure to submit the "pretest" and the "lesson" and the "feedback" forms. Note, there is a not a review for this lesson. Do NOT skip the "tutorial." http://mtsu.edu/~smcdanie/I_cubed/Lesson2/lesson2- Home.htm
14 Ch 5.7: Random Allocation HOMEWORK: AFTER you complete the randomization simulation, read Sect. 5.7 & define Simple Randomization Block (Restricted) Randomization Stratified Randomization Cluster Randomization Note: Skip Section 5.8 for now.
15 Ch 5.9: Observational Studies Two Main Types of Observational Study used to investigate Causal Factors Case-Control (retrospective) Cohort (prospective)
16 Ch 5.10: Case-Control Study Big Picture Identify group with condition (case) Identify group without condition (control) Compare past exposure to factor for the two groups Advantage: relatively simple, quick, inexpensive, valuable with rare conditions Disadvantage: biases can occur Homework: Read 5.10.1 – 5.10.6
17 Ch 5.11: Cohort Study Big Picture: follow-up study Identify group of subjects of interest Follow them to see what happens (Begin with unaffected observations & wait to see what happens) Advantage: careful measurement Disadvantage: could take a long time for a large enough proportion to be affected (expensive), not good for rare conditions Homework: Read 5.11
18 Ch 5.12: Cross-sectional Study All information is collected at the same time (subjects contact once) Descriptive Ex: Surveys Investigation of Associations – an alternative to the case-control and cohort approach Advantage: no recall bias, no loss to follow-up, cheap Disadvantage: Cannot draw clear inference of causality Homework: Read 5.12.
19 Other Ch 5 Homework Read Section 5.13 & 14 Work Homework Problems # 1 -3. Check answers in the back of the book.