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ERIC Number: EJ810369
Record Type: Journal
Publication Date: 2008
Pages: 26
Abstractor: As Provided
Reference Count: 38
ISSN: ISSN-1076-9986
Delineating the Average Rate of Change in Longitudinal Models
Kelley, Ken; Maxwell, Scott E.
Journal of Educational and Behavioral Statistics, v33 n3 p307-332 2008
The average rate of change is a concept that has been misunderstood in the literature. This article attempts to clarify the concept and show unequivocally the mathematical definition and meaning of the average rate of change in longitudinal models. The slope from the straight-line change model has at times been interpreted as if it were always the average rate of change. It is shown, however, that this is generally not the case and holds true in only a limited number of situations. General equations are presented for two measures of discrepancy when the slope from the straight-line change model is used to estimate the average rate of change. The importance of fitting an appropriate individual change model is discussed, as are the benefits provided by models nonlinear in their parameters for longitudinal data. An empirical data set is used to illustrate the analytic developments. (Contains 1 figure, 1 table, and 12 notes.)
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Publication Type: Journal Articles; Reports - Research
Education Level: N/A
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A