Talk:Significance arithmetic

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1 Precise numbers vs. sig. fig.
2 speed of light
3 100 has one sig. fig.
4 rant
5 Broken link(s)

[edit] Precise numbers vs. sig. fig.

The number of significant figures in the number "8" is actually infinite. The number "8." has only one significant figure.

No, they both have just the one. A decimal point which is not followed by some other digit is irrelevant (especially in this font, where it might just be the period ending a sentence). quota

So, technically, 8 x 8 is 64, whereas 8. x 8. is 60.

technically???!

Remember, 8., 8, and 08 all have one significant figure, wherease 8.0 has 2.

OK.

"8", by itself, doesn't have infinite significant figures. You need to know how that number was obtained -- if it was measured, then it has 1 significant figure, if it was counted, then it has an infinite number (if you want to call it that) of significant digits. The obtaining of the number is what's important -- i.e. If I counted 8 matches in each matchbook, and I counted that I have 8 matchbooks, then 8 * 8 = 64! However, if I measured that each candle is 8 cm (to 1 significant digit) long, then if I have 8 candles, 8 * 8 = 6 decimeter of candle, because I only know the measurement to 1 significant digit. When you have a counted number, it has no effect on the number of significant figures you carry. The use of the period after the number is only a convention.

[edit] speed of light

Is the speed of light really a defined physical constant with infinite significant figures? Isn't it simply a measured constant, and therefore have significant figures? Tejastheory 03:25, 31 August 2005 (UTC)

I agree, the speed of light is definitely a bad example.

Also Banker's rounding is most useful when the quantities are exact, but with just a few significant figures more than wanted, such as currency. Generally, a large number of values are more likely to average out any bias, so that's also a misleading statement. Mark Hurd 19:31, 23 September 2005 (UTC)

The speed of light in a vacuum is defined to be 299,792,458 metres per second. --Apoc2400 06:22, 17 November 2005 (UTC)

Speed of light is a constant, but it's still a measured constant. In a lot of physics, 3x10^8 is simply used, yet 3x10^8 does not have infinite significant figures - it is only precise to one significant figure. 07:03, 17 November 2005 (UTC)

The metre is defined as the length of the path travelled by light in absolute vacuum during a time interval of 1/299,792,458 of a second. So the speed of light is exactly 299,792,458 m/s. --Apoc2400 11:24, 17 November 2005 (UTC)

[edit] 100 has one sig. fig.

The part about adding and subtracting sig figs is wrong at the part where it says:

100 + 110 = 210

100, 110 are significant up to the ones place, even though these digits are zeroes. So will the answer.

100 has 1 sig fig, and 110 has 2, therefore the answer would technically be 200. In order to do what they are saying you would have to do 1.00E2 + 1.10E2 = 2.10E2

[edit] rant

This article offers opinions without clarifying that they are. I agree that significant arithmetic is a bit crazy, but isn't this an encyclopedia?

Also, I'd like to suggest making a seperate article for significant digits instead of having it redirect here. I might do it if I have time.

Cheers,

Forezt 23:05, 30 September 2006 (UTC)

I agree. This article is a bit of rant. It would be better to have a clear concise explanation of signicance arithmetic with a note about problems. User:Winterstein 1st November 2006

I just noticed the comment above after redirecting the "significant figures" article here. It seems we've been around this same block very recently. However, please explain why we need a separate article? --Slashme 16:50, 9 December 2006 (UTC)

Word. The inexplicably bitter tone of the now defunct entry on Significant Figures has now snuck into this otherwise promising page, under the "Uncertainty and Error" section. Significance arithmetic obviously has its limitations, but these limitations can certainly be addressed in a more measured tone. In addition, the section claims that "propagation of uncertainty" is the putative topic of the article. To the contrary, the article itself contains the text, "See the article on propagation of uncertainty for these more advanced and precise rules." It seems ungood to have an entry at variance with itself. This entry seems to need a unified explanation of the relationship between truly correct principles of uncertainty-reporting and all imperfect methods of uncertainty approximation. Right now, it's Correct Method Plus Some Approximation Methods on the one side, versus Evil Sig Figs on the other.

ben.mcclure 15:10, 11 December 2006 (UTC)