\chapter{Introduction}

%grammarly checks

StackExchange is a Q\&A platform and consists of 174 communities \cite{stackexchangetour}. 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
% write new numbers about so


In August of 2018, the StackExchange team introduced a small change which 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 \cite{post2018come}. 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 in which direction the community reacts. For this analysis, this thesis utilizes Vader \cite{hutto2014vader}, a sentiment analysis tool, to quantify the sentiments of the answers submitted to questions of new contributors. An interrupted time series is then applied to these values to evalutate 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 number of posts. This includes StackOverflow, MathOverflow, Math, AskUbuntu, SuperUser, and 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, how it works, and shows related work. Section 3 shows the method this thesis uses for analysis. Section 4 contains the investigated datasets. Results are presented in Section 5 and discussed in Section 6. Section 7 conculdes 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
