Summarizing Data

The first step in making evidence-based decisions requires gathering timely, relevant, and accurate data on the issue at hand.  It is then essential to appropriately summarize the data so that they can be used to understand trends, to reveal disparities, or to evaluate programs.   

When dealing with public health problems, we often measure characteristics or attributes on individual people, although if we were studying differences in medical practices across the United States the unit of measurement might be hospitals.  It is always important to be clear about what we are measuring and the unit of measurement in any data collection, analysis, and dissemination of results. 

This course covers:

• Distinguish among dichotomous, ordinal, categorical, and continuous variable types 
• Identify appropriate numerical and graphical summaries for each variable type
• Compute a mean, median, standard deviation, quartiles, and range for a continuous variable
• Determine when the mean is a better measure of central tendency than the median
• Interpret the standard deviation of a continuous variable
• Generate and interpret bar charts and histograms for categorical and ordinal variables 
• Differentiate between a histogram and a bar chart 
• Generate and interpret a box plot for a continuous variable 
• Generate and interpret side-by-side box plots 

Developed by: Lisa Sullivan, PhD; Wayne LaMorte, MD, PhD, MPH