Testing for Parameter Instability using the R/S Statistic

This paper explores the use of the R/S statistic as a means of checking for parameter instability. The nature and properties of the statistic are described, and its behaviour and power in the context of three situations of structural change are examined. The results suggest that the R/S statistic has an ability to detect shifts in means and changes in the intercept of a regression relationship. Moreover, it is more powerful than the OLS variant of the well known cumulative sum of squares residual test for detecting unknown structural breaks in the cases involving the linear regression models that were examined. It would therefore seem to us that the application of the R/S statistic to the problem of testing for structural instability is worthy of further investigation.

Toward a Behaviorally Grounded Theory of Inforrmation Value

Economic models of information value have had little impact on the theory and practice of MIS. This is due in part to difficulties in operationalizing these models, but more importantly, it is due to problems in the theory that stem from descriptively invalid assumptions. This paper examines those assumptions and reviews five major areas for modification: the decision process, human judgment under uncertainty, the choice of actions, multiple information signal resolution, and multiple decisions over time. Incorporation of valid descriptive assumptions in the economic theory wi I I move the field toward a behaviorally grounded theory of information value

An Empirical Examination of a Causal Model of User Information Satisfaction

Users\u27 satisfaction with their information systems is generally recognized as one of the most important indicators of success in designing and implementing computer-based systms. User information satisfaction (UIS) is defined as the extent to which users believe the information systems available to them meets their information requirements. [Ives, Olson, and Baroudi, 1983]The construct is often used as a surrogate for relative information system value because it is more accurately and easily measurable. [Nolan and Seward, 1974] Powers and Dickson [1973] concluded that user satisfaction is the most critical criterion for measuring computer systems success or failure. User information satisfaction has been measured in several ways. Different instruments have been created by Larcker and Lessig [1980], Jenkins and Ricketts [1979], and Gallagher [ 1974]. Recently, Bailey and Pearson [1983] have developed an instrument for UIS that represents an important achievement in the evolution of this construct. Their instrument is broadly based and includes measures of both the system and support quality perceived by the user. Some evidence of the reliability and validity of the instrument has been provided. 77:e Bailey-Pearson U/S Instrument Bailey and Pearson (BP) reviewed 22 MIS studies for factors affecting computer user satisfaction and identified 36 constructs. Three further constructs were added to the list and it was tested for completeness using taped interviews with 32 middle managers. The researchers concluded that there was a 0.99 probability that a mentioned (construct) was on the list (of 39) [Bailey and Pearson, 1983, p. 532]. The thirty-nine constructs are listed in Table I. For each construct, four semantic differential seven point scales were developed and a fifth scale, common to all, asked about the importance of the construct to the respondent. A measure of the response to a construct by a respondent was estimated as the average of responses to the four semantic differential scales for the construct. The general measure of user information satisfaction for a respondent was estimated as the average of the construct estimates weighted by the importance measure of that construct, after having eliminated those for which the response on each of the four semantic differential scales were neutral: Using the instrument, data was gathered from 29 of the 32 managers interviewed during the development of constructs. Analysis of the data led the authors to conclude that the instrument was reasonably reliable and valid. The test sample was quite small and potentially biased since respondents had previously participated in developing the instrument. 1ves, Olson, and Baroudi [ 1983] chose to further study the empirical properties of the Bailey. Pearson (B-P) instrument with an additional objective to develop a shorter version of the instrument. 71:e /ves, Olson, and Baroudi Short Instrument: Ives, Olson, and Baroudi (IOB) collected data from 200 production managers (25 % response rate) in U. S. manufacturing organizations using the Bailey-Pearson instrument and a separate 4-scale instrument of information satisfaction. They performed an exploratory factor analysis on construct scores estimated from the BP data and obtained four significant factors or dimensions, as shown in Table I. Any construct that did not load on one or more factors at the 0.5 level or above was eliminated from a shortened version of the Bailey-Pearson instrument. As well, vendor support which loaded on its own factor was eliminated. Twenty-one of the original 39 constructs passed this test and were included in the shortened instrument. For each of these, two semantic differential scales were retained as well as the importance scale. The results of the factor analysis suggest that a multidimensional structure may underly the user information satisfaction construct. IOB discovered a three factor model of UIS (putting aside vendor support). The factors are: (1) EDP staff and services; (2) the quality of the information product; and (3) the knowledge and involvement levels of the user. Their instrument contains twenty-one questions, each with two semantic differential scales, that measure the three independent factors, but no general measures of user information satisfaction. Their method of arriving at this questionnaire eliminated any general measures of UIS since these measures, by definition, load across all factors. Since this was an exploratory analysis, no evidence was provided as to whether the measures of the underlying dimensional factors achieved convergent or discriminant validity. Evidence was provided that the shortened instrument is a reliable and valid measure ofuser information satisfaction. The 2-scale reliability scores were approximately equal to the 4-scale scores, supporting the claim of high reliability. The general measure of UIS estimated using 21 constructs and the measure using all 39 constructs had a correlation across respondents of 0.9. The correlations of each of these measures with the measure estimated using the separate 4-scale instrument were 0.54 and 0.55 respectively. This evidence supports the claim that the shortened instrument is measuring approximately the same thing as the complete Bailey-Pearson instrument. There are several problems with the evidence provided to support the reliability and validity of the shortened instrument. The reliability estimates obtained are unusually high for this type of instrument, ranging between 0.81 and 0.97 respectively. This evidence supports the claim that the shortened instrument is measuring approximately the same thing as the complete Bailey-Pearson instrument. There are several problems with the evidence provided to support the reliability and validity of the shortened instrument. The reliability estimates obtained are unusually high for this type of instrument, ranging between 0.81 and 0.97. This may be explained in part by a mechanical methods bias introduced by placing all four semantic differential scales on the same page and scored in the same direction. Thus, the analysis of 4-scale, versus 2- scale reliabilities may not be accurate. As well, no estimate was provided of the reliability with which the 21 questions measure the underlying UIS variable. The 0.9 correlation between the 39-construct instrument and the 21-construct instrument may partly be explained by the fact that the two instruments have 21 constructs in common. Just as this correlation is significantly different from zero, it is also significantly different from 1.0 (significant at the 0.001 level). This may be a better test of whether the shortened instrument is significantly different from the Bailey-Pearson instrument. Evidence tha tthe two instruments correlate equally with a third 4-scale instrument is of little help. There is no evidence that the third instrument is either a reliable or valid measure ofuser information satisfaction. Central to the process by which the researchers eliminated constructs from the instrument was an exploratory factor analysis. As they observed, the ratio of sample size to number of scales in the study (7:1) must also be regarded with some caution. . [Ives, Olson, Baroudi, 1983, p. 789]. Thus, one place to begin an analysis of the shortened version of the Bailey-Pearson instrument is by employing the identified factor structure to test the measurement qualities of the instrument. Successful results on this test will support the hypothesized multi-dimensional structure of user information satisfaction. The factor structure obtained by Ives, Olson, and Baroudi is significant not only because they employed it to make decisions about which constructs to eliminate from the shortened instrument. Perhaps more significantly, the factor analysis has yielded underlying dimensions to user information satisfaction that point toward a causal model of UIS. Such a model coutdbe usedas an importantdiagnostictool for information systems builders. Such an important potential development deserves careful study

THE IMPACT OF INFORMATION TECHNOLOGY ON CONTROL: A LEADERSHIP THEORY PERSPECTIVE

In this paper, we explore two models of the impact of Information Technology (IT) on control based on the perspective of leadership theories. The objective is to explain how IT can enhance the control mechanisms in a work group. Review of leadership literature suggests two relevant theories: leadership behavior theory and leadership substitute theory. TO explore these conceptual models, data was collected from 136 managers and professionals who use well-established information systems. The data provides support that ITs impact on control can be explained through its effects on the control factors identified from the two leadership theories. The two models are equally powerful in explaining the criterion variance of control, and the two sets of independent variables from the models are highly correlated, suggesting that either model is good for the study of Irs impact on control. In addition, the data provides support that the impact of IT on control is stronger in dynamic environments. The data also shows that the innovative ability of a work group is positively related to ITs impact on control

Information for monitoring : a simple model of its value and a new determination technique

Thesis (Ph.D.)--Massachusetts Institute of Technology, Sloan School of Management, 1984.MICROFICHE COPY AVAILABLE IN ARCHIVES AND DEWEY.Bibliography: leaves 167-172.by Michael Edmond Francis Treacy.Ph.D

Enabling Organic Methodology through Photoredox Catalysis

Organic methods development has long dictated the molecular scaffolds available to the pharmaceutical and fine chemical synthesis industries. Photoredox catalysis has emerged as a powerful platform to enable novel reactivity with visible light irradiation through triplet sensitization and single-electron transfer. New methods involving radical intermediates are now readily accessible from countless starting materials through the application of these catalysts. Much of my work has utilized established photoredox platforms to enable both nickel catalyzed remote cross-coupling of primary amines via 1,5 hydrogen-atom transfer (HAT) and formal [3+2] synthesis of γ-lactams through triplet sensitization. My further work focuses on the application of ligand-to-metal charge transfer catalysis with cupric chloride and ferric chloride salts towards the alkylation of alkanes through the catalytic generation of chlorine radical to enable HAT. These studies expand photoredox catalysis to inner sphere mechanisms with abundant base-metal salts to enable redox chemistry at reduced electrochemical potentials

Isogonal non-crystallographic periodic graphs based on knotted sodalite cages

This work considers non-crystallographic periodic nets obtained from multiple identical copies of an underlying crystallographic net by adding or flipping edges so that the result is connected. Such a structure is called a `ladder' net here because the 1-periodic net shaped like an ordinary (infinite) ladder is a particularly simple example. It is shown how ladder nets with no added edges between layers can be generated from tangled polyhedra. These are simply related to the zeolite nets SOD, LTA and FAU. They are analyzed using new extensions of algorithms in the program Systre that allow unambiguous identification of locally stable ladder nets