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Less than excellent use of Excel…

July27

Yes, it happened to me – I was using Excel to finish my tax claim and then sent it off to my accountant. He remarked to me, over lunch, that I had made a mistake in my Excel calculations. Yes, I had made the kind of error that is just so easy to do – I had not included all rows in a calculation! This made me sympathize with the following incident…

…It was a simple, but major error – a famous 2010 academic paper, relied on by politicians to confirm their arguments for budget cuts, contained significant errors; and that those errors came down to misuse of an Excel spreadsheet.

2profsHarvard’s Kenneth Rogoff (left) and Carmen Reinhart (right) and are two of the most respected and influential academic economists of today. Or at least, they were! In April, 2013, doctoral student Thomas Herndon and professors Michael Ash and Robert Pollin, at the Political Economy Research Institute at the University of Massachusetts Amherst, released the results of their analysis of two 2010 papers by Reinhard and Rogoff.

During their analysis, Herndon, Ash and Pollin obtained the actual spreadsheet that Reinhart and Rogoff used for their calculations; and after analysing this data, they identified three errors.

xcelThe most serious was that, in their Excel spreadsheet, Reinhart and Rogoff had not selected the entire row when averaging growth figures: they omitted data from Australia, Austria, Belgium, Canada and Denmark. In other words, they had accidentally only included 15 of the 20 countries under analysis in their key calculation.

When that error was corrected, the “0.1% decline” data became a 2.2% average increase in economic growth. A small, but significant Mathematical error when using Excel and hardly to be expected at this academic level? Yes, dear mathematicians, even professors make errors! Full article from SBS here.

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y(y-8) = 9 –> y.y – 8y – 9 =0
–> (y-9)(y+1) = 0, therefore y = 9 (can’t have a distance of – 1 for the other solution for y)
Using the top and bottom of the rectangle,
x = (y-8)(y+2) = (9-8)(9+2) = 11
but, the left side = (x-4) = 11-4 = 7, but rhs = y+? = 9+?, which is greater than the value of the opp. side??
[I think that the left had side was a mistake and should have read (x+4)?]

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