significant figures and measurements

[Genecks]

Would this be two significant figures or three significant figures?

 

 

The middle marks before the 4 and above the 0 are to represent .5 marks.

I got lazy and didn't add in the labels after 4.

 

I'm trying to understand how people use instruments and determine significant figures. After reading my book, I figure it would probably say there are two significant figures: 2.5

 

But from the looks of it, I would say there are three significant figures: 2.55

I'm certain it's above the 2.5, but I'm not sure about anything between 2.5 and 3.0.

 

Would it be better to say 2.50?

 

I can't determine how people figure out the amount of significant figures when looking at something like this.

 

Sure, I'm uncertain about the number between the 2.5 and 3.0. But that doesn't mean I instantly say 2.5, right?

 

If the lazy example for a miniscus was on the 2.5, then would I say there are two significant figures?

[insane_alien]

its going to be 2 significant figures with a rough error of +/- 0.25 -ish.

[Genecks]

Perhaps my understanding of significant figures is still wrong.

 

Would you say it's to be 2.55?

 

Yar. I am confused as to significant numbers within theory vs. real-life measurements.

 

With +/- .25 I assume that means two significant figures: 2.5

 

Thus, it could be 2.75

Or it could be 2.25

 

But doesn't going down from the observed measurement somewhat skew experimental truth?

[swansont]

I don't see where you're getting 2.55. From your picture, it looks to be about 2.7 to 2.8 — more than halfway between 2.5 and 3

 

I'd say it's 2.8 ± 0.2

[jdurg]

In regards to real measurements and significant figures, you're bound by just how precise your measuring instrument is. If you have a ruler that has centimeters and millimeters on it, you're limited to one place after the decimal point and no more since your instrument isn't that precise. (You can have up to 3 significant figures if your measurement is something like 12.8 cm or 128 mm). You can't "create" more significant figures. If you have an imprecise measurement tool, then your figures and calculations are forced to be just as imprecise.

[woelen]

I also would say, this is 2.8, but the margin can be less than 0.2, I would say 2.8 +/- 0.05.