sorry Mike I accidently posted it before i entered in the information I have
reposted the question with some detail
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Thanks

Ruth


"Mike H" wrote:

I think that to get a useful answer you need to provide a bit more than this:-

How do we establish which data relate to the last 30 days?
How are your data laid out, which columns?


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Mike

When competing hypotheses are otherwise equal, adopt the hypothesis that
introduces the fewest assumptions while still sufficiently answering the
question.


"Ruth" wrote:


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Thanks

Ruth