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Part I Analytic study designs - Assignment The following questions are based on the attached paper "Cancer and Tobacco Smoking" (Morton L. Levin, Hyman Goldstein, and Paul R. Gerhardt, JAMA, May 27, 1950, pages 336-338). 1. What study design has been employed (circle one) A. case-control B. Cohort (prospective) C. retrospective cohort (or historical cohort) D. ecologic E. May be either a or c In one or two sentences justify your choice. 2. The comparison group was composed of "those with symptoms referable to the same site but which proved not to be due to cancer." Briefly discuss the appropriateness of this comparison group and its likely effect on the association observed in the study. (3-6 sentences). 3. Histories of tobacco usage were obtained routinely from all admitted patients before the final diagnosis had been established. "This procedure is considered especially important from the standpoint of excluding bias." The authors are referring to bias from: A. selective survival B. cohort effect C. antecedant-consequent confusion D. ecologic fallacy E. selective recall Explain. _____________________________________________________________________________________________ www.sph.unc.edu/EPID168/ © Victor J. Schoenbach Analytic study designs - Assignment - 257 rev. 8/31/1998, 9/5/1999, 9/25/1999
4. The authors state that "There were more than twice as many cases of lung cancer among cigarette smokers as among any other group". Briefly discuss the meaningfulness of this statement. 5. Which interpretation of the data in Table 4 is correct? [Watch out--this is tricky.] A. Cumulative incidence of lung cancer in cigarette smokers* is approximately 2 1/2 times the cumulative incidence in nonsmokers (20.7/8.6). B. Incidence density rate of lung cancer in cigarette smokers* is approximately 2 1/2 times that in nonsmokers (20.7/8.6). C. Prevalence of lung cancer among all cigarette smokers* admitted to Roswell Park Memorial Institute is approximately 2 1/2 times that among all nonsmokers admitted to Roswell Park Memorial Institute (20.7/8.6). D. Prevalence of cigarette smoking* among lung cancer cases is approximately 2 1/2 times the prevalence of nonsmoking among lung cancer cases (20.7/8.6). E. None of the above statements is correct. In one or two sentences justify your answer. __________ *Note: 25 years' duration or longer. Note: The two articles for this assignment were included the packet of copyrighted material sold at the Health Affairs Bookstore. The page numbers jump to reflect the insertion of those pages. Part II The next five questions are based on the attached paper "The Mortality of doctors in relation to their smoking habits", (Richard Doll, Austin Bradford Hill, British Medical Journal, June 26, 1954, pages 1451-1455). The questions are designed to direct your thoughts in reviewing the study. Your answers can be brief! [It is suggested that you read through the entire paper before answering the questions.] _____________________________________________________________________________________________ www.sph.unc.edu/EPID168/ © Victor J. Schoenbach Analytic study designs - Assignment - 258 rev. 8/31/1998, 9/5/1999, 9/25/1999
Page 1 and 2:
Understanding the Fundamentals of E
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Preface Introductory epidemiology c
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Table of Contents Chapter (in Acrob
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1. Introduction Definition, charact
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problems (Schwartz and Carpenter, 1
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HIV - a new or newly-recognized vir
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d = principal investigator's degree
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Analytic studies typically involve
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Observational sciences especially a
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McGavran EG. What is public health?
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2. An evolving historical perspecti
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Time line for the history of public
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as a one-room bacteriology laborato
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− Health surveys − Research fun
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his scientific peers of the correct
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Kuhn, Thomas S. The structure of sc
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3. Studying populations - basic dem
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The demographic balancing equation
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ates. Similarly, bulges in the repr
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When the baby boom cohort retires 1
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The pervasiveness, strength, viciou
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Total fertility rate (TFR) Standard
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Life expectancy The technique, of u
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Excerpt from the U.S. 1993 abridged
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At the other end of the life table,
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to change, hopefully to decline. If
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Thought question: Professors typica
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Descriptive studies and surveillanc
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4. The Phenomenon of Disease Concep
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Classification is the foundation As
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As we gain more sophisticated under
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To recapitulate the above discussio
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Classifying cause of death Since mo
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Laboratory and other objectively me
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distribution but are not diabetic (
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program in the general population,
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Infectious disease Incubation "time
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the direct effects of carcinogenic
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patient outcomes. The design and ev
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detected by screening will appear b
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Morrison, Alan S. Screening in chro
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e relevant. Compromises might be fo
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educational attainment by the numbe
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Distributions - the fuller picture
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Per capita income: Should health ca
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Deaths of children < 1 year of age
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No. of persons with senile dementia
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Incidence Immigration Relationship
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Examples: arthritis, cholelithiasis
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Cohort - entrance into the populati
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Sample calculation: 200 people free
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• The units of time must be state
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Calculation of person-time in a coh
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Original Calculation of person-time
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average risk for a member of the co
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However: Nurses: 601 cases/89,538 w
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treated. If the rate at which patie
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Incidence and prevalence in a popul
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small prevalence. So if the seropre
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Appendix on weighted averages Becau
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Appendix on exponents and logarithm
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and epidemiology. The notation ln(x
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3. For the following hypothetical d
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c. ________________ 6 fatalities /
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Measuring disease and exposure - As
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5. a. Flow Diagram Population of si
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New cases Q ID = ------------------
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Overview 6. Standardization of rate
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differences between the groups in f
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∑ (stratum-specific rates × stan
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especially important when comparing
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copy this cell to the other columns
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where the RR k are the stratum-spec
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and the observed number of deaths i
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Directly standardized rate for A =
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5,022 Indirectly standardized = —
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the situation among older age group
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Appendix on Standardized Mortality
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across age strata, then the damage
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d. How would you feel about the con
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Cases per 100,000 Mean annual incid
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d. dt Indirectly standardized rates
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The second ingredient for an standa
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Group US rate /100,000 County pop.
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Crude rates are comparable because
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The “Big Picture” 7. Relating r
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CHD and oral contraceptives in Brea
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Some basic measures Before diving i
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esophageal cancer? First, if we did
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ought in here as well. When we cont
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Exposure Disease Yes No Total Yes a
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Relation of the odds ratio to the r
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the case-control study estimates th
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If the data had come from a cross-s
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Excess risk = CIR - 1 = 1.0 (i.e.,
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strength of the relationship (e.g.,
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drawn on ordinary graph paper. Howe
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Measures of Impact Concept Relative
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Attributable risk proportion The AR
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show that a large proportion (i.e.,
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Incidence Diagrammatic representati
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1. high frequency of disease 2. pow
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With this diagram and notation we c
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vaguer) “attributed to”. Incide
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Summary There are three categories
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CIR can be directly estimated if th
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I0 I = ——————— 1 + P1
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PD|e PE (RR - 1) PD|e PE (RR - 1) P
Page 217 and 218: Walter, Stephen D. Choice of effect
Page 219 and 220: a. Quit rates were measured as the
Page 221 and 222: 1. Definitions: Relating risk facto
Page 223 and 224: There is an extremely strong associ
Page 225 and 226: 8. Analytic study designs The archi
Page 227 and 228: Progression of types of studies In
Page 229 and 230: Cross-sectional A cross-sectional s
Page 231 and 232: Follow-up studies Along with case-c
Page 233 and 234: of interest community-level influen
Page 235 and 236: ecological approach may be the appr
Page 237 and 238: What measures can be estimated from
Page 239 and 240: Ability to estimate risk Ascertainm
Page 241 and 242: individuals, this relationship does
Page 243 and 244: Odds Ratio (OR) Exposure odds in ca
Page 245 and 246: Simple randomization - assignment o
Page 247 and 248: The relationship of an attribute to
Page 249 and 250: (a / m1) / (b / m1) ad ORe (Exposur
Page 251 and 252: Validity The validity of a case-con
Page 253 and 254: Since the strategic advantage of th
Page 255 and 256: c = f0N1 = number of exposed noncas
Page 257 and 258: experienced the event under study.
Page 259 and 260: approach, the odds ratio computatio
Page 261 and 262: Exposure Yes No Total Cases A B M1
Page 263 and 264: Miettinen, Olli S. The clinical tri
Page 265 and 266: Mantel, N. and Haenszel, W.: Statis
Page 267: Peto, R., Pike, M.C., Armitage, P.,
Page 271 and 272: 5. In contrast to many earlier inve
Page 273 and 274: In this study the use of hospitaliz
Page 275 and 276: Follow-up must be longer for any gi
Page 277 and 278: While acknowledging the very import
Page 279 and 280: world. Even as late as the 1950's,
Page 281 and 282: Causal Inference Direct observation
Page 283 and 284: data on the effects of radiation on
Page 285 and 286: But excluding an explanation based
Page 287 and 288: Strength of the association Pronou
Page 289 and 290: Experimental evidence Certain types
Page 291 and 292: To issue an indictment, the grand j
Page 293 and 294: 10. Sources of error A systematic f
Page 295 and 296: the data in the table. (Note that t
Page 297 and 298: associations. So the same terms may
Page 299 and 300: "Negative bias" - The observed meas
Page 301 and 302: Classifying sources of bias Inspite
Page 303 and 304: The study population is a subset of
Page 305 and 306: This estimate of the prevalence of
Page 307 and 308: unmatched control groups will presu
Page 309 and 310: The odds ratio for this table is 3.
Page 311 and 312: Selection bias in cohort studies Se
Page 313 and 314: Information bias Information bias r
Page 315 and 316: following chapter). The concept of
Page 317 and 318: P h y s i c i a n A Comparison of d
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item). Alpha values of 0.80 are are
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Hypothetical scenario showing effec
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presumably classified as informatio
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Appendix 1 Formulas to see the effe
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Algebraically, _ Pr(E|D') = — the
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Gregorio, David L.; James R. Marsha
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Sources of error - Assignment 1. Th
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Alpha (α) is the probability by wh
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Sources of error - Assignment solut
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3. ii) Selective survival--if OC us
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a. Flow diagram: 1960-1962 1967-196
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Introduction 11. Multicausality: Co
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estimate of what the outcomes would
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A hypothetical example (with apolog
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Questions to ask: There are many as
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Confounding arises from unequal dis
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CHD Incidence by Behavior Pattern a
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In this way, the 1,129 Type A's wit
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exposure. If we assume a baseline r
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Further insight can be gained by co
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Table 7a Colon cancer and drinking
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atio of the observed number of expo
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ural-specific exposure prevalences,
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eing infected, and the more of them
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studies deal with a delimited geogr
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University of Massachusetts at Amhe
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similarly distributed in cases and
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"There have been many important ste
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MAIN POINTS Confounding is a disto
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Greenland, S. and Neutra R.: Contro
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Appendix The following discussion i
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i n1i wi = ----- If exposure is unr
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Multicausality: Confounding - Assig
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4. The following table, published i
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1. Multicausality: Confounding - As
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link between HCS and MI to ensure t
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Multicausality 12. Multicausality:
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Interdependent effects The precedin
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epidemiologic data. Put simply, the
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BP 0 These two lines are parallel;
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ean intake and B representing genet
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Fourth, proportion of disease attri
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Incidence and incidence ratios of f
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% with evidence of impaired red blo
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cancer rate among the light smokers
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Age standardized lung cancer rates
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R11 - R00 = R10 - R00 + R01 - R00 (
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and R111 = R100 × R010 × R001 / (
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R110 = R100 × R010 / R000 (multipl
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Risk ln(risk) 0.19 -1.67 0.13 -2.01
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have clinical or public health sign
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Baseline Characteristics Associated
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Weiss, Noel S. Accounting for the m
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A. Synergism apparently exists in t
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5. Walker (International Journal of
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(or equivalently, the rate for pers
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impact. Synergism in this sense imp
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13. Multicausality - analysis appro
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very far on instruments but needs t
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Summarizing the relationships Often
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We saw in the chapter on effect mod
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So the multiplicative model for joi
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misleading summary. These circumsta
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w1 CID1 + w2 CID2 Summary CID = —
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c d bcn0 + adn1 Var(ln(CIR)) ≈
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Kleinbaum, Kupper, and Morgenstern;
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1 + 1 + 1 3 ORMH = —————
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Risk = R00 + Obesity effect Obesity
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two (or more) factors that "interac
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OR = exp(β3) β3 is the difference
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Other regression models [Optional f
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Know the epidemiologic meaning of t
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14. Data analysis and interpretatio
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and questionable data. Monitoring p
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presence of particular proteins (e.
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4. Count - the number of entities,
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Algorithms - A procedure that uses
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Imputation causes the least distort
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Prenatal exposure to diethylstilbes
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Possible outcomes (Colors of pairs
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In a strict decision-making mode, t
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C = area between -z and +z D = area
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two-tailed 5% significance level).
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If the p-value is not small (i.e.,
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OR we observed was greater than 1.0
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Large trials (e.g., 250 deaths) Tru
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The concept behind the confidence i
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Formulas for confidence intervals f
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Woolf SH, Battista RN, Anderson GM,
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Stallones, Reuel A. The use and abu
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C - Clustered observations, which d
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For example, suppose that n, the sa
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* See previous table Margin of erro
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Even in randomized trials problems
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Pr(H|T) is therefore a function of
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That information gives you pause. C
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Part II 1. In table 2 from the Rose
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If the OR for Current OC use were t
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6. There are no interaction (produc
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24. Submit manuscript from previous
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Cooperative agreement A cooperative
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Assurances by the applicant and her
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The new element is the grant award.
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1. What needs to be done? 2. How lo
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Postaward Final report What to do
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2. maintain close supervision of th
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Publication Epidemiology Working Gr
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Weed, Douglas L. Between science an
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1.3 Specific Objectives of Data Man
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engender a basic conflict between t
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1.4.2 Integration Integrate the dat
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2. Consistency of the protocol's im
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2. Coding of a sample of data forms
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2.3 The steps in the Editing proces
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Although it is rare to use more tha
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The first stages of data analysis s
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have less power to exclude the stat
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greater nonresponse by heavy drinke
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Imputation is then carried out as f
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(normal) distribution in the popula
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Appendix **************************
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___________________________________
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Public health approach The public h
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health, particularly at the world l
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Causative or preventive agents Scur
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Human behavior is also biology The
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crowded, under-resourced urbanized
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Bibliography Annas, George J.; Leon
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18. Overview and Conclusion A look
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Epidemiology is expanding In recen
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More reliance on "soft money" - res
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__________ This is not a new challe
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