Chapter 2 Data 1 Five W s Who What When Where and Why provide context for data a Data Table An arrangement of data where each row represents a case and each column represents a variable i Case An individual about whom or which we have data ii Record Information about an individual in a database b Relational Database Two or more separate data tables are linked together so that information can be merged across them tables are called relations c Spreadsheet Layout designed for accounting that is often used to store and manage data tables 2 Types of Variables the characteristics recorded about each individual or case a Categorical Variable When a variable names categories and answers questions about how cases fall into these categories i Nominal Variables Variables used only to name categories ii Ordinal Values Values can be individually ordered b Quantitative Variable When a variable has measured numerical values with units and the variable tells us about the quantity of what is measured i Units Describe how each variable has been measured 1 How much of something we have or how far apart the variables are ii Time Series Data The same variable measured at regular intervals over time 1 Months quarters years etc iii Cross Sectional Data Several variables are measured at the same time point c Counts Used to summarize the frequency of each case of the CATEGORICAL variable occurring or they can be the values of a QUANTITATIVE variable whose units are a number of something d Identifier Variable There are exactly as many categories as individuals and only one individual in each category cannot analyze these numbers i Example Student ID number neither fully categorical nor quantitative 3 Data Sources a Surveys Polls A study that asks questions of a sample drawn from some population in the hope of learning something about the entire population i Respondents People who answer a survey b Experiments Actively manipulate the variables or factors to see the results i Subjects or Participants People who are experimented on ii Experimental Unit Animals plants websites and other inanimate subjects c Observational Studies A study based on data in which no manipulation of factors has been employed d Data Mining The analysis of large transactional data sets for purposes other than those for which the data were originally collected
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