Statistics is... a collection of techniques for planning experiments, obtaining data, and then organizing, summarizing, presenting, analyzing, interpreting, and drawing conclusions based on the data... statistics uses data to gain understanding, to answer questions… “the science of learning from data”

Process of Statistical Investigation The four-step process: Define the problem, usually by asking questions that need answers. Collect the Data determined to be needed to answer the question posed Analyze the data including numerical and graphical summaries Interpret the results of the analysis, including communication of the results Define the problem Collect the data Process of Statistical Investigation Interpret & communicate results Analyze the data, summarize

Observational study vs. Experiment Read Chapter 1 and review the examples given there and on my website for insight into the statistical process. HW: In your own work, begin to think of your research in terms of this four-step process…you probably already do! Chapter 2 in the textbook addresses the second step, Collecting Data and includes: specifying the objectives of the study choosing the variables to be measured picking an appropriate design for the survey or experiment collecting and organizing the data Observational study vs. Experiment an observational study in contrast to an experiment does not involve the imposition of treatments by the investigator but only observations… example of lead levels in children of parents who work in a battery factory… example of political polling…

There are always potential problems with any type of survey The latter example has data collected through a survey and there are several types of survey sampling discussed in 2.2: simple random sampling where each sample of size n has the same chance of being sampled as any other sample of the same size. stratified random sampling where we first divide the population into strata and then randomly sample within each stratum. cluster sampling involves randomly sampling a block, apt. building, etc. from a city and then sampling every person in the block, building, etc. Consider the example of estimating the number of violent deaths in Iraq… systematic sampling - sample every nth element of the population There are always potential problems with any type of survey nonresponse measurement problems including bad wording of questions, bad delivery of questions, bad memory of the respondents, etc. How do surveys get their data? personal interviews (time-consuming, expensive) telephone interviews (the most popular way with big polling organizations) self-administered questionnaires direct observation

HW for Tuesday: Get the textbook, read 1.1-1.5 & 2.1-2.6. Pay special attention to the examples. We’ll finish our discussion of Ch. 2 next time - note there is lots of terminology here! Get R and SAS and start exploring them a little… http://www.r-project.org/ http://www.uncw.edu/itsd/sassetup.htm