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Use Shift Functions to Illustrate Differential Effects of Treatment
|Posted By: Ross Mitchell on August 23, 2011|
|Thank you for an excellent review.|
In raising your question about whether students entered college as already strong thinkers as measured by the CLA, which required a better discussion of the before and after measures than was provided by the authors, I think it would have been helpful to offer a specific technique for how to communicate this comparison.
In an article published in Teachers College Record (Mitchell & Mitchell, 2005), I used "shift functions" (e.g., Wilcox, 1997) as a graphical, rather than statistical, analysis technique to illustrate this exact sort of comparison in performance across the distribution of performance for a reference point (time or group). I think this would be an excellent tool for depicting the comparison you wished to see.
Ross E. Mitchell
University of Redlands
Mitchell, R. E., & Mitchell, D. E. (2005). Student segregation and achievement tracking in year-round schools. Teachers College Record, 107(4), 529-562.
Wilcox, R. R. (1997). Introduction to robust estimation and hypothesis testing. San Diego, CA: Academic Press.