ABSTRACT
Many of the most interesting research questions in education and the social sciences involve the measurement of change. Often educational researchers want to understand how people develop or change over time. As Willett (1988) rightly points out, “the very notion of learning implies growth and change” (p. 346). Thus, anytime we ask questions about the way in which learning occurs or about people’s growth or decline in some area, we are implicitly asking questions that involve the measurement of change. Such questions might include: How do students’ skills grow over time? Is this growth steady or does the rate of growth change over time? What is the shape of this growth trajectory? Do people (or units) tend to change in the same way over time? Or is there a great deal of variability between people in terms of their rate of change over time? Finally, we often want to understand what factors help to predict the rate at which change occurs, or which variables help us to understand inter-individual differences in the rate of change. In higher education, there are many research questions that involve change over time. Do student grade point averages increase over time? Do the grade point averages of males and females increase at the same rate? To what degree has the diversity on college campuses increased over the last two decades? Why are some universities more successful than others in increasing the diversity on their campuses? With enrollment declines, institutions also ask about the demographics of their student populations for planning purposes. Such questions are best answered using analysis methods that explicitly model change over time.
