GerstmanPP01__培训课件.pptVIP

1: Measurement Basic Biostatistics * Chapter 1: Measurement Basic Biostatistics * In Chapter 1: 1.1 What is Biostatistics? 1.2 Organization of Data1.3 Types of Measurements 1.4 Data Quality Basic Biostatistics * Biostatistics Statistics is not merely a compilation of computational techniques It is a way of learning from data Biostatistics is concerned with learning from biological, public health, and other health data Basic Biostatistics * 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 * Measurement Measurement ≡ the assigning of numbers and codes according to prior-set rules (Stevens, 1946).  Three main types of measurements: Categorical (nominal) Ordinal Quantitative (scale) Basic Biostatistics * Categorical Measurements Classify observations into named categories Examples HIV status (positive or negative) SEX (male or female) BLOOD PRESSURE classified as hypo-tensive, normo-tensive, borderline hypertensive, or hypertensive Basic Biostatistics * Ordinal Measurements Categories that can be put in rank order Examples: STAGE OF CANCER classified as stage I, stage II, stage III, stage IV OPINION classified as strongly agree (5), agree (4), neutral (3), disagree (2), strongly disagree (1); so-called Liekert scale Basic Biostatistics * 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 * 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 occurrence Measure the following variables: Source: Willett et al., 1995 Basic Biostatistics * Measurement Scales Examples (cont.) Smoker (current, former, no) CHD ons