GerstmanPP01

Basic Biostatistics,1,Chapter 1: Measurement,Basic Biostatistics,2,In Chapter 1:,1.1 What is Biostatistics? 1.2 Organization of Data1.3 Types of Measurements1.4 Data Quality,Basic Biostatistics,3,Biostatistics,Statistics is not merely a compilation of computational techniquesIt is a way of learning from dataBiostatistics is concerned with learning from biological, public health, and other health data,Basic Biostatistics,4,Biostatisticians are:,Data detectives who uncover patterns and clues through data description and exploration,Data judges who confirm and ad adjudicate decision using inferential methods,Basic Biostatistics,5,Measurement,Measurement the assigning of numbers and codes according to prior-set rules (Stevens, 1946). Three main types of measurements:Categorical (nominal)OrdinalQuantitative (scale),Basic Biostatistics,6,Categorical Measurements,Classify observations into named categories ExamplesHIV status (positive or negative)SEX (male or female)BLOOD PRESSURE classified as hypo-tensive, normo-tensive, borderline hypertensive, or hypertensive,Basic Biostatistics,7,Ordinal Measurements,Categories that can be put in rank orderExamples:STAGE OF CANCER classified as stage I, stage II, stage III, stage IVOPINION classified as strongly agree (5), agree (4), neutral (3), disagree (2), strongly disagree (1); so-called Liekert scale,Basic Biostatistics,8,Quantitative Measurements,Numerical values with equal spacing between numerical values (like number line)Examples:AGE (years)SERUM CHOLESTEROL (mg/dL)T4 cell count (per dL),Basic Biostatistics,9,Example: Weight Change and Heart Disease,Investigate effect of weight gain on coronary heart disease (CHD) risk 115,818 women 30- to 55-years of age, all free of CHD Follow over 14 years to determine CHD occurrenceMeasure the following variables:,Source: Willett et al., 1995,Basic Biostatistics,10,Measurement Scales Examples (cont.),Smoker (current, former, no)CHD onset (yes or no) Family history of CHD (yes or no)Non-smoker, light-smoker, moderate smoker, heavy smokerBMI (kgs/m3)Age (years)Weight presentlyWeight at age 18,Quantitativevars,Categoricalvars,Ordinal var,Basic Biostatistics,11,Variable, Value, Observation,Observation unit upon which measurements are made, e.g., person, place, or thingVariable the generic thing being measured, e.g., AGE, HIV statusValue a realized measurement, e.g., an age of “27”, a “positive” HIV test,Basic Biostatistics,12,Data Collection Form,Data Collection FormVar1 (ID)1Var2 (AGE) 27Var3 (SEX)FVar4 (HIV)YVar5(KAPOSISARC)YVar6 (REPORTDATE)4/25/89Var7 (OPPORTUNIS) N,Each questionnaire contains an observation,Each question corresponds to a variable,Basic Biostatistics,13,Example: U.S. Census Form,Basic Biostatistics,14,Data Table,Each row corresponds to an observationEach column contains information on a variableEach cell in the table contains a value,Basic Biostatistics,15,Data Table Example 2: Cigarette Use and Lung Cancer,Unit of observation is region, not individual,Variablescig1930 = per capita cigarette use in 1930mortality = lung cancer mortality per 100,000 in 1950,Basic Biostatistics,16,Data Quality,An analysis is only as good as its data GIGO garbage in, garbage outValidity = freedom from systematic errorObjectivity = seeing things as they are without making it conform to a worldviewConsider how the wording of a question can influence validity and objectivity,Basic Biostatistics,17,Choose Your Ethos,BS is manipulative and has a preferred outcome. Science bends over backwards to consider alternatives.,Blackburn, S. (2005). Oxford Univ. Press,Frankfurt, H. G. (2005). Princeton University Press,Basic Biostatistics,18,Scientific