Stanines, Percentiles, and Freedom

by | Jun 2, 2016 | Articles, Assessments, Testing

Learning. It’s not just for our students!  There is certainly a learning curve for the newly revised law.  This is a good thing, however, for through this law we have gained freedom!  Nevertheless, with freedom comes responsibility – the responsibility to learn.

Those parents who have chosen testing for the annual assessment are beginning to realize that stanines are quite different from percentiles.  Although stanines are less precise than percentiles, in many ways they reflect the bell curve much more.  If you recall, the purpose of a standardized test’s norm group is to plot the scores on a bell curve and then draw comparison scores thereafter.  The normal bell curve with its distribution can be referenced above.

Looking closely at the bell curve distribution, you will notice that the 4th, 5th and 6th stanines include a large range of percentile scores.  This reflects the fact that the bell curve is tallest in that middle range:  that those ranges represent the most students.  The 5th stanine contains the most scores – from the 40th to the 59th NPR (Normed Percentile Rank).  A stanine score of 5 is not very precise, but reflects that the student falls right where the largest group of other students do.

In comparison, the 9th stanine includes only 4 NPR scores: 96-99. The 9th stanine is much more discriminating than any other except the 1st. Only 4% of students are expected to score in that stanine distribution.

Be cautious that you don’t assume that the 1st digit of an NPR is reflected in the corresponding stanine rank because that just isn’t true. For example, an NPR of 93 falls in the 8th, not 9th, stanine rank. A 23 percentile rank falls in the 4th stanine, not the 2nd. For those with high scoring students, you’ll want to realize that both the 8th and 9th stanines cover NPR’s in the 90’s: the 8th stanine for scores from 89 to 95 and the 9th stanine for scores from 96 to 99.

Conversely, scores in the 1st or 2nd stanines are particularly low. Only 11% of the student population scores as low. This is why the articles in the scoring section of our website have been changed to help parents whose children are scoring in those low ranges. We highly recommend that parents identify why their students are struggling and search for strategies to help them reach their full potential.

Perhaps you’ve never aspired to understand statistics or bell curves, and you shudder when you see a percent sign! Although we want to help you understand these things, what is truly important is educating our children. The law is definitely a hoop we must jump through to get that privilege, and CHEWV is here, in part, to help you make that jump as painlessly as possible. You must know how to satisfy the law’s requirements and to do so with integrity. While a rudimentary understanding of stanines and percentiles is needful, understanding our own children and educating them to their God-given potential is the higher goal!

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