Clinical Trials

❘❙❚■ Chapter 36 | Use of FiguresIntroductionA graph or figure is a visual illustration of data, where data consist of observationsof one or more variables. Data can be thought of as:• categorical (qualitative)• numeric (quantitative)Categorical data are split into the following three groups:• binary (containing two categories)• nominal (more than two categories with no ordering)• ordinal (more than two categories with inherent ordering)Numeric data are more complicated and can be categorized as:• discrete numeric (takes a whole number in a given range)• continuous (taking any value, not necessarily an integer)• censored (continuous data that can only be measured in a certain range)• other data, such as rates or percentagesGraphs are usually produced post-analysis to provide the reader with a visualunderstanding of the global picture regarding the treatment effect. However, it is alsoimportant to visualize the data prior to its analysis [1,2]. Displaying the databeforehand enables one to see how it is distributed, in addition to spotting anyoutliers, unexpected values, or errors. This provides a prior global interpretation andallows for any corrections that might be required before performing the final analysis.A number of different figures can be employed for visual inspection of the data, butonly well-documented, appropriate figures will illustrate the patterns sufficiently.Basic characteristics of a graphA useful graph displays both the magnitude and the frequency of individual datapoints from the distribution under consideration [3]. A graph should contain atitle, and x and y axes with their respective labels. The x-axis is the horizontal axisand usually corresponds to the independent variable; the y-axis is the vertical axisand tends to relate to the dependent variable. Graphs should be clear and haveshort, informative titles describing the data that are displayed.A useful graph will contain appropriately labeled axes and clearly presentedinformation. The final graph should summarize the data by itself, without the408