Readings about business, economics, operations, and statistics.
And maybe a few other things from time to time.
Wednesday, July 21, 2010
Time series graph
There are lots of time series graphs available, but sometimes there are more issues that you want to include. This is sometimes accomplished with bubble charts, but here's a nice example using geography as the "x-axis":
Saturday, July 17, 2010
Graphs can say one thing, or another
First, I am not posting this to make any statement about Paul Krugman, or anything like that. But when comparing time series data, choosing the starting point can be more imporant than it seems, as this blogger demonstrates. You could imagine investing strategies being compared in a similar fashion. One graph shows strategy A is better, but with the same data and a different start date, another graph would show that strategy B is better.
Another issue is the choice of the other data sets - they can also be chosen to look "fair" but those time series contain special features that make the analysis less than fair. For example, compare company X with specially chosen company Y, because of the special charges for Y in a particular quarter make some observation about X seem more true.
Simple comparisons are not always so simple.
Another issue is the choice of the other data sets - they can also be chosen to look "fair" but those time series contain special features that make the analysis less than fair. For example, compare company X with specially chosen company Y, because of the special charges for Y in a particular quarter make some observation about X seem more true.
Simple comparisons are not always so simple.
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