Dynamic Social Network Modeling and Analysis Workshop Summary and Papers (2003) / Chapter Skim
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The Key Player Problem
The Key Player Problem
Pages 241-252
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From page 241... ...
The second problem, KPP-2, arises in the public health context when a health agency needs to select a small set of population members to use as seeds for the diffusion of practices or attitudes that promote health, such as using bleach to clean needles. In the organizational management context, the problem occurs when management wants to implement a change initiative and needs to get a small set of informal leaders on-board first, perhaps by running a weekend intervention with them.
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Closeness centrality is defined as the sum of geodesic distances from a given node to all others, where geodesic distance refers to the length of the shortest path between two points Thus, a node with a low closeness score (very central) should be able to influence, directly and indirectly, many others.
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From page 243... ...
The Group Selection Issue The group selection issue, discussed as the group centrality problem in Everett and Borgatti (1999) , refers to the fact that selecting a set of nodes which, as an ensemble, solves KPP-1 or KPP-2, is quite different from selecting, an equal number of nodes that individually are optimal solutions for KPP.
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For KPP-2, applicable concepts include vertex covers and dominating sets. A vertex cover is a set of nodes whose members are incident upon every edge in the graph.
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. An alternative approach is information entropy.
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, the distance from a set to a node outside the set can be usefully defined in a number of ways, such as taking the maximum distance from any member of the set to the outside node, taking, the average distance, or taking the minimum distance. For KPP-2, the minimum distance is appropriate since the fact that the distance to an outside node might be large for a given member of the set will usually be irrelevant.
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Empirical Trials The operation of the algorithm is illustrated using two datasets drawn from the public health (AIDS) and military (terrorism)
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From page 249... ...
The selected nodes match our intuition and divide the main component in two big chunks. Turning to KPP-2, we are also interested in selecting a small group of nodes to be subjects of an intervention - specifically, to be trained as peer educators (known as Peer Health Advocates or PHAs)
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consists of a presumed acquaintance network among 74 suspected terrorists. For the purposes of this analysis, only the main component is used, consisting of 63 individuals.
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between the nodes across all possible networks.4 KPP measures based on distance and reachability could then be computed substituting expected distance for observed distance. The practical challenge here Is to find shortcut formulas for expected distance and connectedness that enable fast computation.
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From page 252... ...
In the military context, commun~cation among, actors with redundant skills may sometimes be less important than communication between actors with complementary skills. In the public health context, it is helpful in slowing epidemics to minimize mixing of different populations (such as when married women are linked to commercial sex workers via their husbands)
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Key Terms
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