Comparing Quality Improvement Graphical Tools

¶ … Quality Improvement

Comparison of Graphical Tools used in Quality Improvement

Quality Improvement Tool Comparison Matrix

Quality Improvement Tool

Uses

Bar Graph (StatSoft, 2014a)

Values for a single variable is represented by bars or columns

Each bar represents a single case and the value of the variable (time, temperature, etc.…) is denoted by the Y-axis

Histogram (StatSoft, 2014b)

Graphical representation of a frequency distribution for a variable, with columns or bars representing the distribution of class intervals and the height of the columns representing the frequency of each class

Control Chart (StatSoft, 2014c; Trusko, Pexton, Harrington, & Gupta, 2007, p. 146-149)

Compares the means and ranges for a variable using two line charts, although vertical histograms can be incorporated into the chart as well to facilitate visualization of how much values are deviating from the expected norm

Bar graphs are seemingly ubiquitous, in part because of the inherent simplicity of the data representation. Bar graphs can be used to represent the value of a variable for each case in a series (StatSoft, 2014a). For example, a bar graph can be used to compare the performance values of healthcare quality standards nationally, regionally, and within a health system (U.S. Department of Health and Human Services, 2011). By comparison, a histogram provides a graphic representation of the values for a frequency distribution using bars or columns (StatSoft, 2014b). One example would be to chart the annual length of stay for all adult ICU inpatients at tertiary-care teaching hospitals nationally. The bars would represent intervals of days or hours, while the height of the bars would represent the number of hospitals belonging to that time interval. While the histogram is a type of bar graph, the information it represents is therefore distinct from the information that is represented by a bar graph. If the length of stay data were represented by a bar graph, each bar would represent a hospital, but if the hospitals were to be grouped by length of stay performance then that would be a histogram, if the height of the bars represented the number of hospitals belonging to each performance group.