Categorical variables (or nominal variables)Ģ) Continuous Variables: These are sometimes called quantitative or measurement variables they can take on any value within a range of plausible values. Discrete variables may be further subdivided into: There are three general classifications of variables:ġ) Discrete Variables: variables that assume only a finite number of values, for example, race categorized as non-Hispanic white, Hispanic, black, Asian, other. As a result, it is important to have a clear understanding of how variables are classified. Procedures to summarize data and to perform subsequent analysis differ depending on the type of data (or variables) that are available. Differentiate between a histogram and a bar chart. Generate and interpret side-by-side box plots. Generate and interpret a box plot for a continuous variable. Interpret the standard deviation of a continuous variable. Give an example of when the mean is a better measure of central tendency (location) than the median. Construct a frequency distribution table for dichotomous, categorical, and ordinal variables. Compute a mean, median, standard deviation, quartiles, and range for a continuous variable. Identify appropriate numerical and graphical summaries for each variable type. Distinguish among dichotomous, ordinal, categorical, and continuous variables. Instead, we select a sample from the population of interest, and generalizations about the population are based on the assumption that the sample is representative of the population from which it was drawn.Īfter completing this module, the student will be able to: It is generally not possible to gather information on all members of a population of interest. 
A population consists of all subjects of interest, in contrast to a sample, which is a subset of the population of interest.
When dealing with public health problems the units of measurement are most often individual people, although if we were studying differences in medical practice across the US, the subjects, or units of measurement, might be hospitals. Information consists of data elements or data points which represent the variables of interest. The first step in solving problems in public health and making evidence-based decisions is to collect accurate data and to describe, summarize, and present it in such a way that it can be used to address problems.
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