title: How to detect if change in time series data is no longer significant?
body: <p>I have a set of news articles for which there are stats, eg.: number of twitter posts mentioning the article for range of days. Natural behavior of stats values is that the number of new posts grows fast and then decreases as the news ages.</p>
  
  <p>I would like to know how to calculate the number of days after which the changes to stats are not significant anymore (eg.: &lt;0.1% of total posts) for the whole set of data with some confidence level.</p>
  
  <p>Could you give some hints where to look for information and methods? I'd appreciate some code sample in Python too :)</p>