2The Scientific Method•The scientific method involves competing hypotheses about a natural phenomenon (the “truth”) •Data provide evidence in support of one or more hypothesis •Biostatistics uses data to draw inferences bt thtthabout the “truth” 3The Role of Biostatistics inPublic Health1. Generate hypotheses about the “truth”2.Design a study; collect data3. Descriptive statistics - Look at the data4. Statistical inference•Discover patterns amidst variability •Make an inference about the unknown tthbdthbd d ttruth based on the observed data4
3Biostatistics Paradigm1.Variable - a characteristic taking on different lvalues •“Random” variable: values arise partly as a result of chance2.Response variables vs. explanatory variables 3.Tendency for certain values of one variable to occur together with certain values of another variablevariable •Conditional probabilities•Relative risk - “risk ratio”5Types of Variables1. Quantitative: “amount” •Discrete (gaps) vs. continuous 2. Qualitative: “attribute”•Nominal (no “order”) vs. ordinal 6
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4Bias and Variance1.Variation - differences among measurements •Natural” vs. “measurement” 2.Bias and Variance •Bias: average measurement – truth•Variance: variation about the average 7Descriptive Statistics1 Collecting data1. Collecting data2. Organizing and summarizing data3. Analyzing data4. Interpreting data8