Can you help me with significant digits?

[BassyBill]

And of course we all know Wiki is always right.

The sarcasm is both irrelevant and fallacious. Whether wikipedia is "always right" or not is no guide at all as to the accuracy of the information I quoted. In this particular case, it's spot on.

If, however, you prefer a conventional academic source, then here's one that should meet even the most exacting standards.

Invalid Link Removed

The number of significant figures in a number containing trailing zeros before the decimal point is ambiguous. In the number 5800, if the measurement was made to the nearest unit and is 5800 rather than 5801 or 5799, both zeros are significant.

 

[dmonroe]

Actually the only difference between this and what I've said is the matter of PRECISION. I was assuming that this question was coming from a possible student that was trying to get a grasp on the subject, therefore I was merely trying to help in the initial understanding of the basics of the subject. If he IS ,in fact, a student they will go into precision and its effects on significant digits a little later.

As I said I was merely trying to help.

I meant no offense to you bassybill or anyone else for that matter.

 

[jp58]

The question is oversimplified, I think. There's not enough info in the OP to infer the accuracy of the figures quoted, and so you can't really say how many significant figures there are for that reason. Zeros can be significant or not, depending on the accuracy with which a stated quantity is known.

Exactly 50 (not 49 or 51) people is two significant figures. And exactly 23,000 seconds is five. But the OP doesn't say whether the figures are exact, or not.

I completely looked past that when I read it. I just went with the "generic" rules that I had picked up via osmosis during the various chem classes I've had.

I've gotten into the practice of underlining the "extra" digit I create when I look at a calibrated instrument, and that practice has saved my hind on a midterm and a final. Not to mention professors are typically a little more lenient on students that simplify their jobs.

If I were to have counted 50 people, I would typically write 50.0 as my answer/data point, much in the same way if I counted 23,000 items I would write 23,000.0 (or just go with scientific notation).

 

[BassyBill]

According to every Physics Professor I have come in contact with as well as all of the Physics books I own or have read this is ABSOLUTELY WRONG!

And of course we all know Wiki is always right.

I meant no offense to you bassybill or anyone else for that matter.

No problem. But could I respectfully suggest that when you post in future and "no offense" is meant, then some restraint with the text emphasis, sarcasm and use of rolling eyes smileys will make it much less likely that you actually cause any? Just a thought.

 

[BassyBill]

I completely looked past that when I read it. I just went with the "generic" rules that I had picked up via osmosis during the various chem classes I've had.

I've gotten into the practice of underlining the "extra" digit I create when I look at a calibrated instrument, and that practice has saved my hind on a midterm and a final. Not to mention professors are typically a little more lenient on students that simplify their jobs.

If I were to have counted 50 people, I would typically write 50.0 as my answer/data point, much in the same way if I counted 23,000 items I would write 23,000.0 (or just go with scientific notation).

This would be unambiguous for the number of people as the value can only really be an integer, but in fact 50 would do the job just as well and the figure after the point is redundant. The same would apply to counting 23,000 items (rather than making a measurement).

For the measurement in seconds, greater care would be needed as 23,000.0 is actually one significant figure more than 23,000.

 

[dmonroe]

No problem. But could I respectfully suggest that when you post in future and "no offense" is meant, then some restraint with the text emphasis, sarcasm and use of rolling eyes smileys will make it much less likely that you actually cause any? Just a thought.

Of course. As a matter of fact I just won't use the smileys or text for emphasis at all in the future. To be honest the method you expressed has always made more sense to me anyway. I just also know that in the first physics classes answers expressed in that manner were always counted as wrong or at least some points were deducted. Once again, assuming DLI848 is an early physics student that's what his professor will want.

Before his next test I would suggest he talk to his professor and discuss these counter viewpoints and find out exactly which approach he will be using for grading. Physics professors can certainly be an odd lot. One will tell you one thing and the next may express something completely different using completely different notation as well.

Afterwards if he following this thread maybe he will let us know how it turns out. Personally I would be interested in knowing.

Thanks again for the respectful debate! (no sarcasm intended...btw) I enjoy such matters simply because it's rare that I don't learn something which I always welcome.

Life becomes pointless and at the very least stagnant once we stop learning IMHO.

David

 

[BassyBill]

Physics professors can certainly be an odd lot.

Yes, indeed.

I agree with many of the other comments in your post as well, by the way - especially the ones about learning and also clarifying expectations with instructors.