1. Social Network Analysis
Basic concepts.
Data and analysis.
Example

2. Basic concepts
Social Network analysis (SNA) is the mapping and measuring of relationships between social actors (e.g., individuals, organizations)
Nodes are social actors.
Edges/Ties are the relationships
Egocentric v.s Sociocentric

3. Data Collection Interview, survey, documents, diaries, observations
Sociocentric:
Saturation surveys (with a list of actors or free-recall)
Egocentric
Name Generator and Interpreter: ask the focal actor for names of people he/she is connected with; these alters are interviewed to report their characteristics, their relationships with the focal actor, how do they interconnect with each other.
Concern: accuracy
People are bad at recalling interactions in a specific time frame.
A tie can be denied by an actor.

4. Data Analysis Cohesion: the interconnectedness of actors in a network.
Distance: the number of ties that connects two actors
Reachability: the extent to which an actor is related to others.
Density: # of ties/possible
# of ties

5. Data Analysis
A clique is a subgroup of actors who are directly connected with each other and no additional actor in the network is connected to all members of that subgroup

6. Data Analysis Centrality measures identify the most prominent actors
Degree: # of ties an actor has
Closeness: # of ties that connect an
actor with other all actors
Betweenness: # of times an
actor connects two other actors.

7. The Framingham Heart Study 5124 subjects, 53,228 family/social ties.
Christakis, N. A., & Fowler, J. H. (2008). The collective dynamics of smoking in a large social network. New England journal of medicine, 358(21),
The Framingham Heart Study
5124 subjects, 53,228 family/social ties.
45% were connected through friendship, 39% have coworker(s), 10% has an immediate neighbor.
Centrality; clustering
Findings:
From 1971 to 2000, # of smokers decreased.
Smokers have moved from the center to the periphery of the network.
Smokers are interconnected.
People quite smoking when their friends do so.