SQL Query applying Standard Deviation function...

Hi Experts,

I have below table structure

DECLARE @table Customer (Date DATE, CustomerID VARCHAR(5))
INSERT INTO @Customer (Date, CustomerID) VALUES
('2/6/2015','ADXPA'),
('2/6/2015','AKXLV'),
('2/7/2015','CPDYA'),
('2/7/2015','ZXDQW'),
('2/8/2015','LK1MP'),
etc, till 3836 Records for '2/8/2015' and 4869 Records for '2/8/2015' etc...

Now, I want to take the records which are meeting the standard deviation value of count of CustomerIDs in the group.

I hope below will give you more idea...

Date	Count of Customers	Avg. Count	STD DEV
2/6/2015	2	3944.07	1849.61
2/7/2015	2	3944.07	1849.61
2/8/2015	3836	3944.07	1849.61
2/9/2015	4869	3944.07	1849.61
2/10/2015	4953	3944.07	1849.61
2/11/2015	4913	3944.07	1849.61
2/12/2015	5164	3944.07	1849.61
2/13/2015	4292	3944.07	1849.61
2/14/2015	3463	3944.07	1849.61
2/15/2015	5909	3944.07	1849.61
2/16/2015	4825	3944.07	1849.61
2/17/2015	4490	3944.07	1849.61
2/18/2015	4555	3944.07	1849.61

Here I want to filter out +/- STDDEV of Average - So I need to filter out rows with dates 2/6/2015, 2/7/2015 and 2/16/2015 since these values not in the range of +/- STDDEV of Average.

Here CustomerID is Varchar type, So we need to convert them to Count first partitioning the Date Column and take the average and STDDEV of all without any partition...Correct me if I'm wrong...

Pls. help me with a query as I'm struggling it with for some time.... I appreciate your help.

Pls. let me know if you need more details...

Thanks,

dhamu13