Does subdomain (or sub sub domain) affect analytics data of root site?

[MarketingGroup]

We self-host our public website, but over time have also added  subdomains onto it that are not public and are for internal or even client portals.  I am seeking advice as to whether those subdomains affect the analytics data (self referrals, visits, bounces) of the public site that I am tasked with analyzing.  I feel that it does skew the data but need to build a solid case to move the public website to a new domain, so as to leave the existing one in tact with all of its subs.

[MarketingGroup]

Thanks for taking the time to respond.  The guide on setting up tracking across multiple domains was helpful to learn how to filter referal traffic.  Unfortunately in this case there is a combination of subdomains with tracking code and also others without, as they are intended to be internal.  I am hoping to prove whether having so many is even in some small way negatively impacting the root domain.  This article offered an interesting viewpoint: https://www.pi-datametrics.com/identify-seo-sub-domain-conflict-cannibalisation/

[ChrisAshton]

"Tracking IDs are the unique codes that you're given when you create a Google Analytics property, and look something like "UA-123456-1". Any page with that tracking ID, regardless of the site it's on, will send data to that property." Source

So basically, if you're using that same tracking ID across all subdomains then yes, it will be skewing your data. If you're unsure, the easiest way is to view the source of the page and search for UA- . You'll see a code something like the one quoted above; if it's the same on all subdomains then there's your problem

Your options are to either remove it from the subdomains you don't want to track or check out Eric's guide on how to how to set it up correctly.