\chapter{Introduction}

%grammarly checks

StackExchange is a Q\&A platform and consists of 174 communities\footnote{\url{https://stackexchange.com/tour}}. Each community evolves around a specific topic, for instance, StackOverflow focusing on software engeneering, or AskUbuntu focusing on the Ubuntu operating system. This distincts StackExchange from other Q\&A sites such as \emph{Yahoo! Answers} where no such differentiation into topics exists. %TODO ref

% stackexchange and how it developed via stackoverflow \cite{mamykina2011design} good description of SO
% Design Lessons from the Fastest Q&A Site in the West \cite{mamykina2011design} early investigation of so
% goto place for programming questions (SO)
% social media
% knowledge archive 
% different to top-down forums %TODO success of SO paper
% write new numbers about so %TODO


In August of 2018, the StackExchange team introduced a small change that may have had a huge impact on the platform. They added a new feature to visibly mark questions from new contributors, as part of their effort to make the site more welcoming for new users\footnote{\url{https://meta.stackexchange.com/questions/314287/come-take-a-look-at-our-new-contributor-indicator}}. Specifically, members who want to answer a question created by a new contributor are shown a notification in the answer box that this question is from a new contributor. The StackExchange team hopes that this little change encourages members to be more friendly and forgiving toward new users. 
% write about the change investigated
% stackexchange new contriutor post: https://meta.stackexchange.com/questions/314287/come-take-a-look-at-our-new-contributor-indicator?cb=1
% what did change intend?

This thesis evaluates whether this change has a real impact on the community and if so how the community reacts. For this analysis, this thesis utilizes Vader \cite{hutto2014vader}, a sentiment analysis tool, to measure the sentiments of the answers submitted to questions of new contributors. Furthermore, this thesis includes the votes these questions receive and the number of questions new contributors ask. Interrupted time series are then applied to these values to evaluate whether the change achieved its purpose of making the platform more welcoming. 
% how is change investigated by this thesis
% vader library

This thesis investigates the ten largest communities of the StackExchange platform measured by the number of posts. This includes most prominent communities, for instance, StackOverflow, MathOverflow, Math, AskUbuntu, and SuperUser as well as some lesser-known communities.
% write about other communities (e.g. i investigated)



%write a bit about results

%write about next chapters
The remaining part of this thesis is structured as follows: Section 2 explains StackExchange and its communities, how it works, and shows related work. Section 3 shows the method this thesis uses for analysis in detail. Section 4 contains the investigated datasets. Results are presented in Section 5 and discussed in Section 6. Section 7 concludes this thesis.





%other chapters
% how the new contributor thing works https://meta.stackexchange.com/questions/314472/what-are-the-exact-criteria-for-the-new-contributor-indicator-to-be-shown
