Hi @pspan - thank you for writing into the Community! Since I’m not sure exactly what your chart setup looks like, I’ll try to explain what I think is happening -- 

Amplitude is an event-based platform, which means that events are logged with the event properties and the user properties present at the time the event was fired, and this is what populates in the chart.

Let's say you have a group of users who fired event A, and you are analyzing event A in the Event Segmentation chart. At the time they fired event A, their user property gender had not been updated. But now it is updated. Even though gender is updated now for the users, their gender would pull up as (none) when looking at event A since there was no user property associated with gender at the time event A was activated.

So in your situation, perhaps the users you are excluding (user property: email) do not have this property sent with the event you are querying on, which is why they are populating in the chart.

I'd recommend taking a look at these articles to dig deeper into this topic:

1. How Amplitude updates user properties
2. Community: Event-Based Analytics

Please let me know if you have any questions!

@jmagg Is there a reason behind why this happens? After reading your provided articles, it is clear how Amplitude updates properties, but I am running into a similar situation as @pspan. When a user fires the same event on different instances, they may or may not have their UserID assigned to them. In other words, when a user opens our app on a certain day, they might have a UserID assigned. However, when they open the app (thus firing the same exact event) they are not assigned a UserID. It is very confusing and leads to unreliable data.

Hi @mpAVO - I think it might be best to explore this further in a Support ticket! I’ll ask the Community Admin to create a ticket for you, and I’ll be in touch next week.

I’m working with Amplitude support to investigate.  Will update here based on the results.  

While the links provided are a helpful overview of user-based properties and event-based analytics, they do not directly address the problem we’ve run into.  

Our Saved Segment is a list of internal users we want to exclude.  The list is based on User ID -- a primary key that exists for all users and does not change.  We don’t know why a subset of the excluded users appears in charts.  This makes reporting unreliable -- and is undercutting confidence in Amplitude within our org.

@pspan - have you had the chance to review the email I sent you last week?

@mpAVO - I’ll be messaging you via email right now!

@jmagg is a rock star!  She helped us dig into the data to find the specific events where user id was missing for a user we intended to exclude.  We now understand why excluded users were sporadically appearing in our charts -- this happened any time user id was missing for the event in question.  We’ll work with our developers to ensure user id is consistently passed to Amplitude.    

Thank you for the kind words @pspan & glad we got to the bottom of this!