First time I can recall seeing a reference to a Control (process behavior) chart in the local paper. Expect that it will be more common over the next 25 years.
Test you knowledge in assessing “scores and trends” ?
ISTEP+ Scores: It Depends, On How You Look at Them, by Jeff Abbott, Ph.D., J.D., published in the Indianapolis Star, Dec 23, 2008.
The public does not understand the statistically valid way of analyzing ISTEP+ test scores.
To repeat, it is of little statistical use to compare only one year’s test results with the previous year’s results. It is a meaningless comparison, particularly given the fact that the reported scores are from different groups of students, and that the tests compared are not even the same tests.
Test scores must be compared instead over a period of years to determine the trend of the scores. This can be done using an Excel spreadsheet, plotting the scores, preparing a line graph, and then adding a trend line.
The resulting chart shows that ISTEP+ scores for Indiana students are not dropping over the long run but are increasing. The linear trend line is going up from left to right, which indicates a positive trend in scores. Moreover, by using a widely used quality-process tool called a “Control Chart” it can be shown that the scores are increasing because of something other than random chance. (An upcoming issue of the Indiana Policy Review will explore this finding in depth.)
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