cluster grouping

Examples of cluster grouping in the following topics:

• Optional Collaborative Classrom Exercise

  • Create a cluster sample by considering each state as a stratum (group).
  • By using simple random sampling, select states to be part of the cluster.
  • Then survey every U.S. congressman in the cluster.

• Three sampling methods (special topic)

  • The population is divided into groups called strata.
  • The strata are chosen so that similar cases are grouped together, then a second sampling method, usually simple random sampling, is employed within each stratum.
  • We break up the population into many groups, called clusters.
  • In the middle panel, stratified sampling was used: cases were grouped into strata, and then simple random sampling was employed within each stratum.
  • In the bottom panel, cluster sampling was used, where data were binned into nine clusters, three of the clusters were randomly selected, and six cases were randomly sampled in each of these clusters.

• Lab 2: Sampling Experiment

  • The student will demonstrate the simple random, systematic, stratified, and cluster sampling techniques.
  • NOTE : The following section contains restaurants stratified by city into columns and grouped horizontally by entree cost (clusters).
  • Pick a cluster sample of restaurants from two cities.

• Sampling Techniques

  • Sometimes it is more cost-effective to select respondents in groups ("clusters").
  • Clustering can reduce travel and administrative costs.
  • Instead, clusters can be chosen from a cluster-level frame, with an element-level frame created only for the selected clusters.
  • Cluster sampling generally increases the variability of sample estimates above that of simple random sampling, depending on how the clusters differ between themselves, as compared with the within-cluster variation.
  • Panel sampling is the method of first selecting a group of participants through a random sampling method and then asking that group for the same information again several times over a period of time.

• Clustering tools

  • Tools>Cluster>Hierarchical proceeds by initially placing each case in its own cluster.
  • This results in clusters of increasing size that always enclose smaller clusters.
  • "farthest neighbor") computes similarities between the member of the new cluster that is least similar to each other case not in the cluster.
  • This gives a clear picture of the similarity of cases, and the groupings or classes of cases.
  • The E-I index is often most helpful, as it measures the ratio of the numbers of ties within the clusters to ties between clusters.

• Clustering similarities or distances profiles

  • Cluster analysis is a natural method for exploring structural equivalence.
  • Tools>Cluster).
  • The second panel shows a rough character-mapped graphic of the clustering.
  • The dendogram can be particularly helpful in locating groupings of cases that are sufficiently equivalent to be treated as classes.
  • The measures of clustering adequacy in Tools>Cluster can provide additional guidance.

• Clusters of Neuronal Cell Bodies

  • A nucleus can either by a relatively compact collection of neurons or a distinctly identifiable group of neurons spread over a large area.
  • In neuroanatomy, a nucleus is a brain structure consisting of a relatively compact cluster of neurons.
  • In addition, nucleus can refer to an identifiable distinct group of neurons that can spread over an extended area.
  • In the peripheral nervous system, a cluster of neurons is called a ganglion.

• Classification and Categorization

  • So for example, under conceptual clustering, your mind has the idea that the cluster DOG has the description "animal, furry, four-legged, energetic."
  • Conceptual clustering brings up the idea of necessary and sufficient conditions.
  • Different clusters have different requirements, and objects have different levels of fitness for different clusters.
  • Different objects can fit a cluster better than others; fuzzy-set theory is not binary, so it is not always clear whether an object belongs to a cluster or not.
  • Categorization can also be viewed as the process of grouping things based on prototypes.

• Value Clusters

  • People from different backgrounds tend to have different value systems, which cluster together into a more or less consistent system.
  • Certain values may cluster together into a more or less consistent system.
  • A communal or cultural value system is held by and applied to a community, group, or society.
  • Some sociologists are interested in better defining and measuring value clusters in different countries.
  • Their responses are aggregated and can be used to reveal regional value clusters, like those displayed in this map.

• Boranes: Boron-Hydrogen Compounds

  • The boranes comprise a large group of compounds with the generic formula of BxHy.
  • The larger boranes all consist of boron clusters that are polyhedral, some of which exist as isomers.
  • For example, isomers of B20H26 are based on the fusion of two 10-atom clusters.
  • closo- (from the Greek for "cage") a closed complete cluster (e.g., icosahedral B12H122−)
  • reaction of a nido-borane with an alkyne to give a carborane cluster