SNA and case study about SNA

Brief introduction of SNA

Social network analysis [SNA] is the mapping and measuring of relationships and flows between people, groups, organizations, computers, URLs, and other connected information/knowledge entities. The nodes in the network are the people and groups while the links show relationships or flows between the nodes. SNA provides both a visual and a mathematical analysis of human relationships. Management consultants use this methodology with their business clients and call it Organizational Network Analysis[ONA]
To understand networks and their participants, we evaluate the location of actors in the network. Measuring the network location is finding the centrality of a node. These measures give us insight into the various roles and groupings in a network -- who are the connectors, mavens, leaders, bridges, isolates, where are the clusters and who is in them, who is in the core of the network, and who is on the periphery? 

case study of SNA

(a) Describe the above social network according to your best knowledge.
(b) Within this social network, who is the most influential? (What SNA measurements you learned from the lectures can help you to solve this problem? Why you choose those measurements? Show the readers how you identify this person by computing the corresponding indexes.)
(c) Suppose you are conducting a research on the social network of these five students and the above results are obtained, discuss the findings and their implications based on your data.

From the above relation graph, we can see that besides Eva, the other four people are all closely connected.  For Eva, she only connects with David. we can see David has one of the best locations in the network -- He is between two important constituencies. He plays a 'broker' role in the network. Thus Eva does not belong to the 4 heavy connected social network.Without David, Eva would be cut off from information and knowledge in the four people network.

I choose the  Between Centrality to explain why David is the most influential one in the network. Between Centrality is expounded in the lecture as "Between Centrality is a measure of the potential for control as an actor who is high in “betweenness” is able to act as a gatekeeper controlling the flow of resources (information, money, power, e.g.) between the alters that he or she connects"A node with high betweenness has great influence over what flows -- and does not -- in the network. David may control the outcomes in a network. That is why they say, "As in Real Estate, the golden rule of networks is: Location, Location, Location

we consider the five persons can be represented by a matrix.And the degree centrality can be easily got as (L=6,g=5),the density of the network is 2L/g(g-1) = 0.6

	Alice	Bob	Carol	David	Eva
Alice	-	1	1	1	0
Bob	1	-	0	1	0
Carol	1	0	-	1	0
David	1	1	1	-	1
Eva	0	0	0	1	-

We use the formula below to calculate the betweenness.

It can be normalized as C’B(ni) = CB(ni)/[(g-1)(g-2)/2]

we have 

	Betweenness centrality
Alice	0.14
Bob	0
Carol	0
David	0.58
Eva	0

Therefore, from the calculation, David has the largest value in Betweenness Centrality. 

The outcome reflect that David is the most influential in the network and Alice is the second one. 
If Bob and Carol want to connect to Eva ,they must go though Alice and David.For david,The good news is that he plays a powerful role in the network, the bad news is that he is a single point of failure.