We were fortunate enough to have Sam Awezec, Senior Marketing Manager at HubSpot, join us virtually to discuss running expirements in HubSpot at our June meetup.
After our meetup, Sam provided me with some resources to share with everyone.
This free web tool by Optimizely makes it easy for marketers to determine how large of a cohort they need to expose to an experiment for it to return statistically significant results.
This free web tool by VWO makes it easy to determine if an experiment that's already running has reached statistical significance.
This article goes over how and why we unsubscribed 250,000 people from our blog due to graymail and why it helped. Also, for the HubSpot customers in the audience graymail suppression is now a feature within HubSpot. If they're interested in how they can use it, the steps can be found here.
As for the specific question after the talk "what criteria did we use to determine who to unsubscribe". The criteria we used was: hasn't clicked on an email in 6 months or more months and their subscription date was greater than 120 days ago. After the success with this, we've since gotten stricter with our blog subscribers and we now look at SSLE (Sends Since Last Engagement) and if a monthly blog subscriber reaches a value of 30 (meaning they haven't clicked within the last 30 emails we've sent them) then we unsubscribe them and for our daily subscribers at a value of 20.
In addition, here is a copy of the Growth Presentation.
I hope this is helpful and we look forward to seeing you at future meetups!