Chromatography Forum

Hi All,
we are in the process of installing and validating Empower and have hit a snag.

During a dissolution analysis we have reported the individual results for each vessel as whole number %. So far so good, however when we use a custom field to calculate the mean of those results it uses an unknown number of decimal places, which gives a different mean to that calculated by hand.

Is there a way of forcing Empower to calculate a mean from the rounded results ( I know everyone is screaming about intermediate rounding! but we have to report each vessel and the mean of all six.)

Cheers

Mike

I would suggest using duplicate columns - one w/ precision set to 3, one set to 0.
when checking calculations, use the 3 place column and then make sure your means match when rounded to a whole percentage point.

I'm pretty sure that there is a way to truncate things, but I'd strongly advise against it.
When an auditor has a go at your numbers, he/she will start with your standard concentration and all of your peak areas. They will likely compute to however many decimal places and then round to the precision set in Empower. They will probably carry at least one decimal place into the mean calculation. If you use truncated values, you run a very real risk of rendering results that are not easily reproduced by calculator.

If you insist on pursuing this path to data perdition, search help for:
Precision and rounding in custom calculations

Hi Mike,
DR is right with using caution on rounding too early, but by
your comment:

( I know everyone is screaming about intermediate rounding! but we have to report each vessel and the mean of all six.)

you already know this!
and it seems your are comparing results already calculated this way.

so to use the rounded values, simply use the ROUND(fieldname,0) in your custom field to round to 0 decimal places. This will instruct your calculation to use the rounded value of the field for your summary fuction.

e.g.
AVE(ROUND(fieldname,0))

Where fieldname is replaced with the field name you want to average.

Best regards,
Ben