Clinical Trials

❘❙❚■ Chapter 36 | Use of FiguresFigure 5. Dot plots to show the change in CD4 cell counts from baseline to the end of 48 weeks’ follow-upfor patients in the MaxCmin 1study.1,000CD4 count change: baseline to week 48 (cells/mm 3 )5000upper quartilemedianlower quartile–500Indinavir/r (n = 142) Saquinavir/r (n = 130)r = ritonavir.Treatment armHowever, the median and IQR can be difficult to calculate if the dataset containsa large amount of data.If we take a look at the baseline age of patients who initiated SAQ/r inthe MaxCmin 1study, a stem and leaf plot can be drawn as shown in Figure 6.With a little effort, you can see that the age range is 19–71 years, the medianbaseline age is 39 years, and the IQR is 34–48 years. Unfortunately, stem and leafplots are not visually appealing and are therefore not used that frequently inmedical literature.Box plots for showing central location and outliersA box plot, or box and whisker plot, is a diagrammatic representation of continuousdata. It provides a visual means of exploring the skewness of the data and allowscomparisons to be made between two or more groups. However, it only illustratesthe median, IQR, and range, rather than all of the data individually. A basic boxplot consists of a rectangle (the box) with arrows (the whiskers) extending outfrom the top and bottom. A box plot contains a ‘+’ or horizontal line within thebox to indicate the median. The bottom of the box corresponds to the lower414