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J. G. Kreifeldt

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Publications by J. G. Kreifeldt (bibliography)

1993

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Kreifeldt, J. G. and Nah, K. (1993): Charts for Simplified Bivariate Anthropometric Design. In: Proceedings of the Human Factors and Ergonomics Society 37th Annual Meeting 1993. pp. 416-420.

“Generalized workspace and clothing design problems often arise in which two anthropometric constraints must be considered simultaneously in order to accommodate some specific target percentage of the population. In the theoretical (and unlikely) instance in which the two variables are perfectly positively correlated, the problem is readily solved using univariate percentile information. However, in the more realistic case in which the two variables are less than perfectly positively correlated, bivariate percentile charts are required. These bivariate charts are rarely available but may be computer-generated from the univariate data and the correlation between the variables after assuming some appropriate bivariate distribution (usually Gaussian). However, such computer access is not always available especially when a quick estimate is needed. This paper presents a simplified approach to bivariate design based on the workable assumption that the bivariate target percentage will be met by using the same (to be determined) univariate cutoff value for each variate. This cutoff value depends on the target percentage value and on the degree of correlation between the variables and the assumption that the data are adequately represented by a Gaussian bivariate distribution. The method takes advantage of simple charts prepared expressly for this purpose and several of which are presented herein. The method also has utility in a number of practical and common problems as well as being suitable for student use.”

1989

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Kreifeldt, J. G., Levine, S. L. and Iyengar, C. (1989): Reduced Keyboard Designs Using Disambiguation. In: Proceedings of the Human Factors Society 33rd Annual Meeting 1989. pp. 441-444.

“There are a number of important applications where the accuracy of typed copy is less important than other criteria, such as the speed of entry, ease of learning, reduced keyboard size, provision of innovative keyboard designs and work methods, etc. Some of these applications include communication devices for the motor handicapped and rough drafting. The applications in question still provide single finger typing as opposed to multifinger entries for chord keyboards. One approach to keyboard design for such applications involves using a multicharacter set. Because there is more than one character on a key, the number of keys can be reduced to a point limited only by the required accuracy of the text produced which is itself limited by the ability of "disambiguation" algorithms to decode the ambiguous text strings. Reducing the number of keys increases test entry rates and reduces learning time. Experiments with keysets of 10, 12, 14, and 16 keys have produced keystroke rates of 3.3 to 1.7 characters per second and a 6% keying error while the”

1988

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Kreifeldt, J. G., Levine, S. H. and Chuang, M. C. (1988): Weber's Ratio, Multidimensional Scaling and Incomplete Data Sets: New Light on an Old Problem. In: Proceedings of the Human Factors Society 32nd Annual Meeting 1988. pp. 1183-1187.

“Sensory modalities exhibit a characteristic known as Weber's ratio which remarks that when two stimuli are compared for a difference: (1) there is some minimal nonzero difference which can be differentiated and (2) this minimal difference is a nearly constant proportion of the magnitude of the stimuli. Both of these would, in a typical measurement context, appear to be system defects. We have found through simulation explorations that in fact these are apparently the characteristics required by a system designed to extract an adequate amount of information for an incomplete observation data set according to a new approach to measurement.”

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