In order to create buckets, we use the customer trait createdBy.eventId which is a guid.
A GUID is an acronyom that stands for Globally Unique Identifier, they are also referred to as UUIDs or Universaly Unique Identifiers - there is no real difference between the two.
A guid can contain the characters 0123456789abcdef (hex)
So, to create a bucket, we use a regex to make a selection on the first letter of the eventide, to split into a possible of 16 buckets
Bucket A regex a|b.* will select any customers who have the trait createdBy.eventId with the first letter of the eventide as a OR b
Bucket B regex is c|d.*
Bucket C regex is e|f.*
Therefore 2/16 (2 characters out of 16) = 1/8 = 12.5% of the customers (assuming the eventIds are random, which they are)
Bucket A is 12.5%
Bucket B is 12.5%.
Bucket C is 12.5%
The remainder bucket regex is [0-9].* and is 10/16 = 62.5%
You would create 3 versions of the email, send to buckets A,B,C – wait for a period of time, see which has highest open or click, then send that version to the remainder.
You can have as many test buckets (or just 2) as you want, you change the regex accordingly.