Clinical Trials

Clinical Trials: A Practical Guide ■❚❙❘Figure 4. A pie chart to show the distribution of protocol-defined virological failures for the indinavir/ritonavirarm of the MaxCmin 1study (n = 158).2% 2%Died19%Withdrew consentLost to follow-upVirologically77%r = ritonavir.change in CD4 cell count from baseline to the end of 48 weeks of follow-up(Figure 5).Dot plots can be used for both discrete and continuous data, but continuous datatend to be grouped, otherwise it can be cumbersome to plot the data and the plotbecomes messy and hard to understand. These plots can contain a line that isperpendicular to the data points to show the median value and, similarly, lines canbe included to represent the interquartile range (IQR). Multiple dot plots can bedrawn alongside each other to allow comparisons to be made between groups.Stem and leaf plotsA stem and leaf plot is a hybrid between a graph and a table. It is used for numericdata. This type of graph is usually drawn with a vertical stem and horizontal leaves.The vertical stem consists of the first few digits of the values arranged in numericalorder, while the horizontal leaves are represented by the last digit(s) of each of theordered values. Note that each of the digits in the leaves represents one datapoint. The resulting stem and leaf plot looks similar to a rotated histogram.The advantages over a histogram are that:• Stem and leaf plots are easy to draw by hand.• Individual data values can be read from the graph, including the range,median, and IQR.• They are useful for small datasets.413