Comments on: Excel charts: how to lie or not http://seekerblog.com/archives/20080830/excel-charts-how-to-lie-or-not/ Seeking reliable, objective sources on economics, foreign-policy and energy-policy issues. Thu, 08 Jan 2009 22:35:06 +0000 http://wordpress.org/?v=2.3.2 By: Steve Darden http://seekerblog.com/archives/20080830/excel-charts-how-to-lie-or-not/#comment-28932 Steve Darden Mon, 01 Sep 2008 11:41:19 +0000 http://seekerblog.com/archives/20080830/excel-charts-how-to-lie-or-not/#comment-28932 In your examples, including the origin obscures the content. In such cases, I understood the author's advice was to use line or XY-scatter charts, instead of bar charts. Because bar charts were only suitable for presentation of "variables that are <a href="http://en.wikipedia.org/wiki/Level_of_measurement#Ratio_measurement" rel="nofollow">measured on ratio scale</a>s". Does that make sense? In your examples, including the origin obscures the content. In such cases, I understood the author’s advice was to use line or XY-scatter charts, instead of bar charts. Because bar charts were only suitable for presentation of “variables that are measured on ratio scales”.

Does that make sense?

]]> By: Will Howard http://seekerblog.com/archives/20080830/excel-charts-how-to-lie-or-not/#comment-28931 Will Howard Mon, 01 Sep 2008 09:01:56 +0000 http://seekerblog.com/archives/20080830/excel-charts-how-to-lie-or-not/#comment-28931 Yes but no. Forcing the y-axis origin to be zero, in the author's bar-chart example is not necessarily a good, or necessarily a more honest, idea. The range of 2.5 in the density example may be significant, and if so it may be more misleading to plot the data with a y-axis origin of zero as this would visually underrepresent the variability. Same principle applies to the x-axis of a chart. In time-series, of course the origin and scale of the x-axis are chosen depending on what interval or process one is trying to represent. Following the suggestion of a zero-origin rule literally, a chart of the last ten years' of any financial data set (say, the DJIA) would have to start at the year Zero A.D.?!?! In which case the chart would be unreadable, in itself a potentially misleading representation. Yes but no. Forcing the y-axis origin to be zero, in the author’s bar-chart example is not necessarily a good, or necessarily a more honest, idea. The range of 2.5 in the density example may be significant, and if so it may be more misleading to plot the data with a y-axis origin of zero as this would visually underrepresent the variability.

Same principle applies to the x-axis of a chart. In time-series, of course the origin and scale of the x-axis are chosen depending on what interval or process one is trying to represent. Following the suggestion of a zero-origin rule literally, a chart of the last ten years’ of any financial data set (say, the DJIA) would have to start at the year Zero A.D.?!?! In which case the chart would be unreadable, in itself a potentially misleading representation.

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