For this worksheet, the only thing you have to do is read this paper. This paper deals with the foster care system and it provides a nice walkthrough of IV methodology and how to think about it. Enjoy!
http://mitsloan.mit.edu/shared/ods/documents?PublicationDocumentID=5656
Doyle_JN_2013_cysr_Causal Effects of Foster Care ungated.pdf475.2KB