using Avg()

I have a table with a column named SwErr (Switch Error) with int values
date with datetime values and SwID with char(3)
I am trying to get a subset back where the folowing is true

select the avg(SwErr) for the last 30 days where SwId = 'XX1'
Select the value of todays value of SwErr where SwId = 'XX1'
if todays value of SwErr is greater than 4 times the SwErr Average return in
the value

TIA

Mark Connelly

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