It is well known that the functions in Excel are poor. See for instance
www.npl.co.uk/ssfm/ssfm1/validate/testing/excel.html. #NUM usually means
that the algorithm Excel is using has crashed. Other than obtaining and
using add-ins that work I know of no way round this.
Sam Ellis
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> -----Original Message-----
> From: A UK-based worldwide e-mail broadcast system mailing list
> [mailto:[log in to unmask]] On Behalf Of Christopher Fergusson
> Sent: 24 September 2002 14:06
> To: [log in to unmask]
> Subject: Excel Bug
>
> Hi ALLSTATers,
>
> I am trying to calculate the approx 95% confidence intervals for the
> standardised incidence rate of certain cancers using Byars
> approximation.
> I have a spreadsheet set up in Excel to calculate this manually. The
> formula to calculate it, as set up in Excel, contains the following:
>
> CHIINV(0.025,2*AQ7+2)
>
> where AQ7 represents the sample size.
> Now for most sample sizes this works fine, however for certain sample
> sizes
> (for example 409)the calculation returns the answer #NUM.
>
> Has anybody else come across this in the past, and if so, how is it
> bypassed.
>
> Thanks in advance,
>
> Christopher D Fergusson
> Trent Cancer Registry
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