Significant Figures with Experimental Values

[i_love_science]

Homework Statement

I have a group of experimental numbers: 0.320, 0.910, 0.030, 0.070, and 0.080. I have to add another number to this group, which is also an experimental value. Which one should I use: 0.738, 0.740, or 0.74?

Relevant Equations

sigfigs

I was thinking of choosing 0.740, because it looks the most consistent with the other numbers because they all have a trailing zero. But then, in accordance with sig figs, 0.74 is the right answer. Which one should I choose?
Thank you so much!

 

[hutchphd]

It depends upon the measurement . If the previous numbers are appropriately reported on the same apparatus, then 3 sig fig is still appropriate. But I don't know which value.

 

[phinds]

in accordance with sig figs, 0.74 is the right answer

No, it is the right answer only if you declare that your equipment only produces that degree of accuracy. If you know that it produces 3 significant digits then a trailing 0 is a significant digit.

 

[haruspex]

Did you obtain all of these readings, or did someone else record the existing ones? It is very suspicious that they all have a trailing zero - unless there is some inherent discreteness in the exact values.

Each value should be recorded with the precision it merits. If you are confident your new reading is between 0.7375 and 0.7385 then record it as 0.738.

 

[berkeman]

I have a group of experimental numbers: 0.320, 0.910, 0.030, 0.070, and 0.080. I have to add another number to this group, which is also an experimental value. Which one should I use: 0.738, 0.740, or 0.74?

I know this is a semi-old thread, but hopefully the answer was that you should re-do the experiment. That's a terrible spread of measured values. Look for loose screws or something in your measuring apparatus...

 

[haruspex]

I know this is a semi-old thread, but hopefully the answer was that you should re-do the experiment. That's a terrible spread of measured values. Look for loose screws or something in your measuring apparatus...

They are not necessarily readings of the same underlying value. Maybe points on a graph.