![]() The box and whisker plot shows the following noteworthy statistics of data: median, maximum and minimum values, and upper and lower quartiles. Above, one can see that the individual data points in the 20-29 range are represented most often (four times) in the stem and leaf plot below. The stem on the left displays the first digit(s) and the leaf on the right displays the last digit. Furthermore, a stem and leaf plot shows individual data points, resembling a table, whereas a histogram does not. The key difference between this plot and a histogram is that a stem and leaf plot can be constructed manually without the use of analytical software. Stem and leaf plot is a frequency graphic less utilized but worth considering as a rapid approach to analyze and display data. Pareto Charts are discussed in more detail by Alan Picarillo in the June, 2020 edition of MITE QI/PS Hot Topic. Above is an example of a Pareto Chart exemplifying the descending order of category data and the cumulative total trend line. ![]() When a bar chart presents the categories of data in a descending order of frequency and the cumulative total is represented by the line, this is known as a Pareto Chart. What’s more, a bar chart shows the comparison of categorical discrete variables as opposed to number ranges. However, as depicted above, the histogram has no spaces between the bars. The columns or bars in a histogram and bar chart can vary in height and shape. Above is a simple example of how a dot plot can be applied.Įach column or bar of the histogram represents the frequency of occurrence of quantitative continuous data (y axis). Dot plot, when applied for small data sets, can be used for both continuous and discrete data sets. A dot plot is a graphical representation of data utilizing dots plotted on a simple scale. If the sample size is less than 30, a dot plot is preferred. ![]() If the data size is too small, the histogram may not accurately display the distribution. These graphics should be constructed utilizing a sample size of at least 30 data points. The histogram utilizes rectangular vertical bars to depict where most of the data occurs. It also shows the spread of the data set (x axis) while capturing the presence of outliers or gaps in the data points. Histograms showcase the frequency of continuous data values (y axis) by displaying the distribution or “shape” of a data set. Below are examples and applications of frequency plot graphics. ![]() The goal is to compare the differences between groups, and/or to study the relationships between variables and values. height, weight, temperature, length) and graphics for attribute data, which is data that can be counted and given a whole numerical value (e.g. There are graphics for continuous data, which is data that can take any value (e.g. The frequency graph one chooses depends on the type of data to be analyzed. There are at least six frequency plot methods which one can choose. Frequency plots provide graphical display of data sets that reveal associations and relationships. Visual tools to analyze trends and patterns in quality are powerful aids to achieve continuous improvement. Graphic displays of data offer insights that lists of numbers alone cannot. The adage, “a picture is worth a thousand words” carries significant weight when embarking on a quality improvement opportunity.
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