How to find the overall avg and compare each row (line item) to it

Question

I'd really appreciate any help on this:

1. Background on my data: [Date] (down to hour level), [Volume] -> Volume is equivalent to SUM[Number of Records]
2. How do I find the [avg volume (for each line item - each hour of each day) + std.dev (volume - for each line item - each hour of each day)] and then compare it against each hour of each day

So if each line item > (avg + std.dev) then it should say "ITEM A", Else "ITEM B"

Then, when I make a table: Date, Volume, Item - it should say whether each hour of each day is ITEM A or ITEM B

What I have tried:

IF [Volume] > (AVG([Volume])+STDEV([Volume])) THEN "ITEM A"ELSE "ITEM B"END

Errors I am getting:

• AVG is being called with (table), did you mean float
• Tables can only be aggregated and only using COUNT function
• STDEV is being called with (table), did you mean float
• Can't compare table and integer values