a confusing thing!!

[qabawe]

hello everybody....

i got a small problem in understanding the defference between these 2 terms( Precision and Accurancy), in terms of chemistry

 

 

so, i will be greateful if someone can explain it to me.

[Glider]

I don't know about chemistry, but I can tell you the difference between the two terms.

 

Precision relates to the resolution of a measure. For example, a thermometer graded at 10 degree intervals is less precise than one graded at one degree intervals, which in turn is less precise than one graded in 0.5 degree intervals (and so-on) although they all may be accurate.

 

Accuracy relates to the degree to which a measure reflects the true magnitude of that which it is measuring. For example, a thermometer placed in a beaker of water at exactly 30 degrees C but which reads 20 degrees C is not showing the true magnitude of what it is measuring and so is inaccurate.

 

A measure can be precise, but still inaccurate. A thermometer in the same beaker which reads 20.62745 degrees C is precise, but inaccurate.

 

A measure can be accurate but imprecise. A thermometer graded in 10 degree intervals placed in the same beaker may show something like 'between 25 and 35 degrees C'. This is accurate, but imprecise.

 

Another thermometer placed in the same beaker and reads 30.0000 degrees C is both accurate and precise.

 

A thermometer placed in the same beaker but which reads 'Thursday' is invalid.

[qabawe]

Thank u very much for replaying me, Glider, i almost understand it. and let me say it in my words:

when we do measurements we get several values, called uncertinity in Measurements. if these values are close to each other we call it precious, but it may not be accurate. and todetermine weather a value is accurate or not we should have or we should be given the true value. and the closer the measured value to the true one, the more accurate it is.

[ciderminx]

ive always found these diagrams the best way to understand it.....

http://techniques.geog.ox.ac.uk/mod_2/week_1/lecture-1.htm

[akcapr]

prision is how much u can repet ur result, how repeatable it is

[jdurg]

Yup. I remember the dart board analogy too. Best way to see the difference.

[Glider]

Thank u very much for replaying me' date=' Glider, i almost understand it. and let me say it in my words:

when we do measurements we get several values, called uncertinity in Measurements. if these values are close to each other we call it precious, but it may not be accurate. and todetermine weather a value is accurate or not we should have or we should be given the true value. and the closer the measured value to the true one, the more accurate it is. [/quote']

That's about it.

prision is how much u can repet ur result, how repeatable it is

No, that's reliability.