The Irrelevance of Vertical Scales to Understanding Student Growth

Center for Assessment staff meeting · September 1, 2015

The Irrelevance of Vertical Scales to Understanding Student Growth — Center for Assessment staff meeting, September 1, 2015.
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September 1, 2015

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Staff session
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  1. THE IRRELEVANCE OF VERTICAL SCALES TO UNDERSTANDING STUDENT GROWTH Damian W Betebenner National Center for the Improvement of Educational Assessment Dover, NH September 1st, 2015
  2. “It is a common misconception that to measure student growth in education, the subject matter and grades over which growth is examined must be on the same scale—referred to as a vertical scale. Not only is a vertical scale not necessary, but its existence obscures fundamental concepts necessary to understand growth.” Me Norm- and Criterion-Referenced Student Growth
  3. “If you can’t solve a problem, then there is an easier problem you can solve: find it.” George Pólya Mathematical Discovery on Understanding, Learning, and Teaching Problem Solving, Volume I
  5. A Math Story Problem • Whose high jump changed more? Explain your answer. • Whose high jump change is more remarkable? Explain your answer. • Which high jumper improved more? Explain your answer.
  6. A Math Story Problem Properties that don’t hold with simple examples will not hold in complicated situations. This simple example illustrates how minimally helpful a scale is to understanding change. • A vertical scale allows one to answer a very narrow question: Who changed more? • Remarkable & improvement need not be synonymous with change. • This example (ratio scale, no measurement error) illustrates that a vertical scale is of little help in answering substantive questions.
  7. “One Year’s Growth” If “one year’s growth” is to be useful as a value that makes points on the score scale more meaningful, it would be useful to know if the empirical average value of “one year’s growth” is very different for students at different levels of the score scale or from different demographic backgrounds. Because values for “one year’s growth” are not currently available, the answers to these questions are unknown. David Thissen Validity Issues Involved in Cross-Grade Statements About NAEP Results