At the store, the accountants track the following data on a daily basis:
- count of receipts
- total value of receipts
based on 5 different receipt value ranges
- Less than $5
- $5 to 10
- $10 to 15
- $15 to 20
- over $20
and calculate the Average $ per Receipt.

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The operations department needs to be able to investigate any "non-normal" days.
So, the operations manager wants to be told when the Average $ per Receipt is outside of 1 and 2 standard deviations based on the customer flow (or # of receipts).

Notice that Day 3 Average $ per Receipt of $10.26 will be apparent for 3-4000 receipts, but the accountant wont notice that day Day 4 may need to be identified as needing review.

How do I calculate the Standard Deviation on the Average $ per Receipt by each threshold of customer flow?

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NOTE: I am having difficulty attaching the file of 11 days of data. I will retry after starting this thread.

Thanks in advance for your knowledge.