# Flow block in Amazon Connect: Distribute by percentage
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This topic defines the flow block for routing customers randomly to a queue based on a percentage.

## Description
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+ This block is useful for doing A/B testing. It routes customers randomly based on a percentage.
+ Contacts are distributed randomly, so exact percentage splits may or may not occur.

## Supported channels
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The following table lists how this block routes a contact who is using the specified channel. 


| Channel | Supported? | 
| --- | --- | 
| Voice | Yes | 
| Chat | Yes | 
| Task | Yes | 
| Email | Yes | 

## Flow types
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You can use this block in the following [flow types](create-contact-flow.md#contact-flow-types):
+ Inbound flow
+ Customer queue flow
+ Outbound Whisper flow
+ Transfer to Agent flow
+ Transfer to Queue flow

## Properties
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The following image shows the **Properties** page of the **Distribute by percentage** block. It is configured to route 50% of contacts to the test branch.

![\[The properties page of the Distribute by percentage block.\]](http://docs.aws.amazon.com/connect/latest/adminguide/images/distribute-by-percentage-properties.png)


## How it works
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This block creates static allocation rules based on how you configure it. Internal logic generates a random number between 1-100. This number identifies which branch to take. It doesn't use current or historical volume as part of it's logic.

For example, say a block is configure like this:
+ 20% = A
+ 40% = B
+ 40% remaining = Default

When contact a is being routed through a flow, Amazon Connect generates the random number. 
+ If number is between 0-20, the contact is routed down the A branch.
+ Between 21-60 it's routed down the B branch.
+ Greater than 60 it's routed down the Default branch.

## Configured block
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The following image shows an example of what this block looks like when it is configured. It shows two branches: **50% test** and **50% default**.

![\[A configured distribute by percentage block.\]](http://docs.aws.amazon.com/connect/latest/adminguide/images/distribute-by-percentage-configured.png)


## Sample flows
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Amazon Connect includes a set of sample flows. For instructions that explain how to access the sample flows in the flow designer, see [Sample flows in Amazon Connect](contact-flow-samples.md). Following are topics that describe the sample flows which include this block.
+ [Sample flow in Amazon Connect for A/B contact distribution testing](sample-ab-test.md)