Hi All,

I've got a sheet on which we measure and log the quality of water on a day to day basis. The percentage error for the machine depends on the reading that was given (see below for the specifics). I'm not sure how to get this information into error bars, and have been told by the powers that be, that they won't accept the chart unless it has error bars on it.

+/-10% error at 2.25 ppm
+/-20% error at 0.75 ppm
+/-30% error at 0.20 ppm

I believe that in order to do this, i'll need a calculation to work out the percentage error dependant on the value that's been entered, and then the entire thing put into an 'if' statement.

Any ideas?

Thanks!