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In my experience, the obsession with correct significant figures is an american high school thing. Why should you deliberately have to choose a number that is n
by phreeza 6y ago
In my experience, the obsession with correct significant figures is an american high school thing. Why should you deliberately have to choose a number that is not your best guess? Ideally you should include confidence bounds, but if you don't, it shouldn't imply that you are confident to that level.
- jfim 6y agoBecause it gives an idea of what range is expected for the actual price. If someone gets an estimate of "about fifty bucks" versus "about $51.04", their reaction to seeing a final price of say $62.17 would be different. The first one implies that it's a rough estimate, while the second one doesn't.
- phreeza 6y ago"About" is doing a lot of work, too, no?
- throwawayfire 6y agoIf someone said "about fifty bucks" and it turns out to be $62.17, I'd immediately understand them to be scamming me.
- jfim 6y agoReally depends on what the context is. Maybe for a taxi ride when negotiating a price ahead of time, but pointing at an object, asking for its price, getting an estimate that's off, then getting the actual price before the transaction is completed doesn't feel like a scam.
- Scipio_Afri 6y agoPlease price estimates for car repairs in dollars and cents and state it's only an estimate all the time.. with variations possible depending on what's discovered that might have been missed it that particular context.
- adrianmonk 6y agoThat's definitely where I learned that it was expected. I look at it as one of many possible conventions for communicating precision. For what it is, it works well. But it's not universal, and people who do and don't use it should both keep in mind that the other group exists.
- Gibbon1 6y agoWhen I was getting my engineering degree too many significant figures would earn you -2 pts.
- lb1lf 6y agoMeasure with a micrometer. Mark with a chalk. Cut with an axe. (Apparent practice at a workshop I used to frequent.)
- Gibbon1 6y agoOld crusty semi-retired engineer I knew said when he was young he liked designing things to close tolerances. But once he was old he found more pleasure in designing things that worked with really shitty tolerances.
- lb1lf 6y ago-I had a colleague once, fresh out of mechanical engineering at the local univerity college, who as his first project did a locking pawl for a winch drum. Tolerance? H7. The fitters threw a fit trying to make that happen.
- throwaway0a5e 6y agoClearly he wasn't working in any sort of mechanical capacity while getting that community college degree.
- nullc 6y agoYep. The weird thing is that their sigfig rules of thumb aren't particularly accurate and after any non-trivial operations (or more than a few operations) just give wrong results. Tracking precision through calculations requires interval arithmetic, which is a pretty big PITA and not frequently used. I think the sig figs cult comes out of mistaking a simplified lesson on precision for a useful practice.
- LasEspuelas 6y agoNot sure exactly what you mean. It is well known that you should keep additional digits throughout the calculation and then drop non-significant ones for final results.
- nullc 6y agoThe number of digits out is only a simple function of the digits in if you're doing fairly trivial calculations. Checkout https://en.wikipedia.org/wiki/Interval_arithmetic https://en.wikipedia.org/wiki/Interval_arithmetic for what it takes to monitor precision through complex calculations (in particular, see the bits about using the taylor expansions of non-trivial functions).
- kortilla 6y agoIt hints that someone doesn’t understand these confidence values at all. Why $47.10 and not $47.1032471?