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Conclusion Obvious?
3/15/2013 8:08:00 AM
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Thanks for the study, Brent. Was this an Hypothesis-Driven study or a Data-Driven study? I'm a scientist, not an engineer, but I do use spreadsheet calculations to do quick statistics on very small collections of preliminary data. To analyze experimental results I go a bit deeper and use either MathCAD or Mathematica depending on the preference of my collaborators. For measurements and signal processing I use test-driven software development guidelines to produce code in National Instruments LabVIEW. I use a spreadsheet to document quick calculations that I used to perform with a handheld calculator.

I would hypothesize the use of spreadsheets to analyze mission-critical data would be widespread in business and financial applications. Is it that widespread in science and engineering?

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Platinum
Test Data
3/15/2013 9:31:25 AM
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You have to keep in mind that creating a spreadsheet is much like a creating a software program.  You wouldn't trust a program without running test data through it, and you really have to do the same with a spreadsheet.

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Re: Test Data
3/15/2013 2:00:44 PM
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Thank you very much for the very informative article, actually I have some bad experience with spreadsheets, But my mind did not like to believe that it is with the spreadsheets fault always in my side. Now I know what has gone wrong.

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Platinum
Re: Test Data
3/15/2013 2:05:05 PM
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Tekochip yes I also with you but my problem is when we changed the data sometimes sum functions has changed without knowing me. Is there a any method of locking the formulas after checking the test data.

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Blogger
91% error rate
3/15/2013 5:54:01 PM
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Ninety-one percent of spreadsheets contain errors? The nice thing about handheld calculators (and sliderules before that) was that the engineer was more connected to the calculation. There's a subtle disconnect when doing the calculation in software on a spreadsheet, which makes it easier for a resulting number to gain a couple of zeroes and still not be noticed.

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Platinum
Re: 91% error rate
3/16/2013 2:57:38 AM
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Charles normally we always depend on the spreadsheets, If it is contain 91% errors what will be the best option to overcome this issue.

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Blogger
Re: 91% error rate
3/17/2013 2:22:50 PM
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Charles, one could as easily say 91% of hammer-driven nails are bent.  The thrust of that statement would be powder-gun or electric-gun driven nails go in straight.

91% of nails may be bent by hammer-wielders, but that doesn't mean they don't hold just as well as the gun driven ones.

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Blogger
One has to question the source
3/17/2013 2:36:44 PM
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The author of the blog references a book by Chad Jackson and thoughtfully provides a link to it.

According to https://twitter.com/ChadKJackson, Mr. Jackson is the president and principal analyst of Lifecycle Insights.

Lifecycle Interests refers to the same e-book at this link: http://www.lifecycleinsights.com/solving-engineerings-calculation-compromise-ebook/

However, Lifecycle Interests does not seem to host the e-book on its own website.  The book instead is hosted at the web site of this blog's author, PTC.  The author's company does not host its own work?

One has to question the source for the conclusions of the blog (and by inference the book as well).

I don't necessarily disagree that spreadsheets can cause errors to propagate because they tend to hide the equations.  It does not negate their incredible usefulness.  Other commenters have already noted the need for testing and checking.  ANY tool needs that.  The software being pushed by the blog author needs it just as much.  It may make the process simpler, and add some helping hand, but it also needs to be checked.

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Platinum
3/18/2013 9:25:33 AM
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Years ago, when slide rules were still found in desks and calculators roamed the earth, my mentors gave me this advice:

"If you find that you can't do your initial estimates with a basic scientific calculator, STOP. If you find yourself digging out your textbooks and writing equations, STOP. --You are probably about to make a huge mistake.

"Someone before you has probably seen this problem and has an acceptable plant equation or rule of thumb that you can use. If you reinvent that wheel, the chance that you will make a mistake is very high. You should use those text books to validate or invalidate an approach, not to create new ones, unless the old approaches are clearly inadequate somehow and you are really treading on new territory."

And in the years since, I have used those textbooks to create new approaches, but only in a handful of cases.

The point about spreadsheets is much the same: If someone has written and validated software, USE IT. The chances of making a mistake when modeling with a generic tool such as a spreadsheet or writing your own modeling software are VERY high.

As engineers we have an obligation to our employers, clients, and to the public to get the correct answers. If there is prior art that you can use to help you in this process, USE IT.

Jake Brodsky

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Gold
At least you can see the formulas
3/18/2013 10:06:30 AM
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There is a skeptical side of most engineers that demands to verify everything and assume very little. Last time I checked - (unless the spreadsheet is locked) formulas are easily visible and we can see how values are being calculated.  I prefer that scenario over feeding values into a software "black box", shaking it a bit and then accepting the answer.

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