Understanding variation in you data, and getting comfortable with what that variation does and does not mean is crucial for meaningful improvement. Too much for one episode, I'm splitting Episode 3 into two parts to have more manageable chunks of info to process. And hopefully after both parts, you will be ready to one of two things. Either take every Year-over-Year or Pie chart you are handed and throw it in the trash or, take that as an opportunity to say "can I get the data that went into this chart broken down into time sequence" and start showing people what real QI looks like!