[yerbutnobutyer]

hello!
i was wondering if anyone knew how to calculate the TOTAL % error. ive just finished a titration and im writing my analysis, ive calculated the individual % errors for each piece of equipment that was used eg:pipette. However i dont know how to calculate the overall % error . Id be really grateful for any help.
thanks sarah x

[Mitch]

look up something called "error propagation".

[Donaldson Tan]

given A = B x C, then the error of A is:
dA/A = dB/B + dC/C

[mithrilhack]

you expect him to do derivatives?

[Mitch]

You can't do error propagation without derivatives, more generally partial derivatives.

[hmx9123]

If you know what the individual errors are, you can add them up without doing derivatives in most cases.  Unfortunately, it involves some math that I can't recall at the moment.  There's different procedures for additive, divisive, etc. errors, so it depends on how you're manipulating the data.  Look in a statistics book or just search the web for 'additive errors' or 'adding errors'.  It's in my analytical chem book, but that thing is 2100 miles away from me right now (a worthy place for it).

[Mitch]

You typically just can't add errors though. Additive error addition involves the square root( of the sum of the individual errors individually squared.) But, it all depends on the setup of course.

[pkothari13]

why not take the average of all your experimental values needed to titrate your solution and then find the percent error from the literature value.

or try standard deviation

hope that kinda helped

[sammyr]

percentage error =       (Error / Reading) x 100

[arcanineghost]

at our high school you calculate the percent error by taking the absolute value of the actual/theoretical value - experimental data all divided by the actual/theoretical value times 100%

Looks like this:

|actual-experimental|
-------------------------   x 100% = experimental percent error
          actual


hope that helps