M. Anthony Wong

The results of an exploratory study of patterns of purchase influence in the metal-working industry are reported. The data set used was a representative sample of 2151 purchase influencers in the metalworking industry. Respondents reported their involvement or noninvolvement in each of seven phases of the purchasing decision process. The authors show the presence of identifiable patterns of reported involvement in the organizational buying process and suggest an approach for analyzing those patterns.

Summary Due to the lack of development in the probabilistic and statistical aspects of clustering research, clustering procedures are often regarded as heuristics generating artificial clusters from a given set of sample data. In this paper, a clustering procedure that is useful for drawing statistical inference about the underlying population from a random sample is developed. It is based on the uniformly consistent kth nearest neighbour density estimate, and is applicable to both case-by-variable data matrices and case-by-case dissimilarity matrices. The proposed clustering procedure is shown to be asymptotically consistent for high-density clusters in several dimensions, and its small-sample behaviour is illustrated by an empirical example.

Abstract A hybrid method for clustering multivariate observations is proposed, which combines elements of the k-means and the single-linkage clustering techniques. One purpose of the proposed method is to discover the high-density clusters given a random sample of size N from some underlying population; a high-density cluster at level c in a population with density f is defined as a maximal connected set of points x with f(x) ≥ c. This clustering procedure is practicable for very large numbers of observations and is shown to be consistent, under certain regularity conditions, in one dimension.

In this study, the myoelectric activity of 12 paraspinal muscles of ten men aged 18-24 was recorded to examine the effects of backrest inclination and lumbar support in relation to driving. In total, 24 test conditions were evaluated over a 3.5-hour period in a single day. These tests were then repeated, changing the sequence over the next 4 days. The results indicate a complex interaction between the thoracic and lumbar regions of the back with the lowest myoelectric activity position of 120 degrees backrest inclination, 5 cm of lumbar support, and 13.5-18.5 degrees of seat inclination. Electromyogramatic (EMG) evidence of fatigue was not identified over a 3.5-hour period. The generally low levels of EMG activity and, presumably, disc pressure present in any seating position suggest that the paraspinal muscle activity may not play the predominant role in disc herniation as it relates to automobile driving.