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2012-02-23 23:31:46

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  1. What is internal validity?
    The degree to which the results of a study are attributable to the treatments rather than the flaws in the research design.
  2. What's external validity?
    The extent to which the conclusions of the study are correct for persons beyond those who were investigated
  3. What is reliability? What is reproducibility?
    Reliability = repeatability, tightness of the range of data values in the same laboratory

    Reproducibility = method yields same result accross laboratories
  4. Describe case-series (descriptive)
    Case series = Description about a group of UNIQUE people, leads to the generation of hypotheses that may be subsequently investigated in case control, prospective cohort, cross section or experiential studies
  5. What are the pros and cons regarding case series?
    Pros: simple, no protocol, clinician only, inexpensive

    Cons: investigator bias possible, no hypothesis testing, no masking, no hypothesis testing
  6. Describe Case control (retrospective)
    Retrospective backward looking study that analyzes previous events to find causes, association and risk factors of the dz. Longitudinal.

    • Examine CASES and CONTROLS
    • How did they get sick/stay well?
  7. Pros and cons of case control?
    Pros: quick, inexpensive, best for rare dz, best for identifying the cause of sudden outbreaks

    Cons: recall bias/missing information
  8. Prospective Cohort Study?
    longitudinal study

    aim at identifying risk factors, natural history, incidence of disease

    Study looks at incidence of dz and risk factors
  9. What are the pros and cons of a prospective cohort study?
    • Advantages: Good for multiple outcomes
    • Disadvantages: bad for rare dzes, timely bias due to follow up, expensive
  10. Retrospective cohort?
    Looks at past at a group that was treated similarly to determine outcome
  11. Pros/Cons of retrospective cohort?
    Pros: good for determining risk factors/associations, easy, inexpensive

    Cons: biased from incomplete records, confounders
  12. What's the difference between case control and retrospective cohort?
    • Retrospective Cohort:
    • 1) looking forward in time from time of tx
    • 2) pop = cohort receiving different treatments
    • 3) how did they progress?

    • Case control
    • 1) looking backwards
    • 2) pop not a cohort
    • 3) how did they get sick/stay well?
  13. What's the difference between a controlled and uncontrolled case study?
    Controlled: one new drug tx compared to another drug/procedure that's either a placebo or an accepted tx (gold standard tx)

    Uncontrolled: new tx is described but not compared to anything else
  14. Experimental Study Groups: what is a concurrent control group?
    • A group treated similarly to the test group in the same
    • time frame (sham surgery)
  15. Hawthorne effect is ________
    • Hawthorne effect: when subjects change
    • their behavior just bc they are in a study
  16. What are 3 ethical concerns with clinical trials in research?
    Should not compare to an inferior tx

    Should not w/hold treatment known to be effective

    Patients must sign informed consent form stating risks of participation
  17. What is a Meta-Analysis?

    hint: Meta means later and more highly organized
    • A Meta-Analysis uses published data from several studies to produce one grand overall conclusion
    • --> pooling different sources
  18. What is a sample?
    A group of people representative of the population
  19. Statistical integrity is dependent on the obtainment/collection of a __________
    Truly random sample
  20. Random samples provide you with results with ________ probability of which you _____make inferences concerning the population of interest.

    Non-random samples provide you with results with _______ probability of which you _____ make inferences concerning the population of interest.
    Random: known, can

    Non-random: unknown, cannot
  21. T/F Method of sampling is vital to the determination of probabilities associated w/ various outcomes
  22. Describe the process of randomization in the selection of subjects for a clinical study.
    • Population of interest -->
    • random selection of subjects -->
    • sample population -->
    • inclusion/exclusion criteria -->
    • informed concent obtained -->
    • random assignment -->
    • subjects enrolled in study
  23. Describe the 4 different types of samples and whether they're random or not.
    Simple Random = selection of one unit does not affect the selection of another, each unit has an identifier number, each unit has an equal chance of being selected

    Sequential/systemic random sample= selection of one unit does influence the selection of another, i.e. the first one is chosen randomly and then after that every 17th unit is chosen.

    Randomized block study: subjects/units organized into blocks, once a block is randomly chosen, all those units/subjects are in the study, this is NOT a truly random sample

    Convenience sample: non-random sample, no element of random sampling, external validity seriously questioned (SCCO student research is usually convenience sample)
  24. What elementary school grades are required by lawmust to have vision screenings?
    1st, 3rd, 6th
  25. Describe the goal of the Orinda study and what was developed through it.
    o Population: screened 1163 children in grades 1–8

    o Goal: design the least expensive, least technical, most effective school screening program

    o Modified clinical technique = VA, r’scopy, CT, color vision, ophthalmoscopy (VRCCO)

    Effective in identifying more than 90% of kids w/ RE/binocular vision problems

    90% sensitivity (test + = disease +)
  26. Describe the VIP STUDY: vision in preschoolers
    Goal: determine best methods to screen for major eye conditions by nurses + lay personnel

    • Part I--> screening vs comprehensive evaluation
    • 2 screening tests used = 2/3 sensitivity for RE, but for more complicated problems (high RE, amblyopia, aniso) it was 90% sensitivity

    Part II --> Preschoolers had comprehensive evaluations and then screenings done by nurses and lay people. Outcome = nurses and lay people had about the same 85% sensitivity. Results were similar to the results from comprehensive exam. CONCLUSION: VISION SCREENINGS FOR CHILDREN DO NOT NEED TO BE CONDUCTED BY LISCENSED PROFESSIONALS
  27. What is specificity and what is sensitivity?
    Specificity = ability to detect true negatives

    Sensitivity = ability to detect true positives
  28. Describe an ROC curve
    ROC curves: maximize sensitivity + specificity

    • ROC = receiver operator characteristic curve
    • x = false positives (1 – specificity)
    • y = true positives (sensitivity)

    Use different tests or combinations of several tests to provide largest area under curve

    Maximum area under the curve (1.00) yields maximum sensitivity + specificity
  29. Incidence = _______
    what is incidence as a ratio?
    probability of developing a certain condition over a period of time

    new cases/population at risk (standardized number i.e. 100 ,1000, 10000)
  30. Prevalence = ______________
    Probability of people having a particular dz at a given time

    existing case of dz/total population at risk (standardized number i.e. 100, 1000...)
  31. What is point prevalance?

    What is period prevalance
    prevalence at a point in time

    prevalence at a point and new cases recurrence within a period of time
  32. Prevalence vs Incidence

    1) Which one has a time component?
    2) Which one is preferred when discussing dz etiology? When studying health services utilization?
    • 1) Incidence
    • 2) Incidence, Prevalence
  33. CLEER study = ?
    SEE study = ?
    CLEER = study of refractive erro over time in specific ethnic grous

    SEE = study of dry eye