How to use MAP scores as part of an Individual Education Plan
Districts and states provide guidelines about how to compute progress for Special Education students. One way is to use standard scores; the distance of an individual’s score from the mean score in standard deviation units. This would make sense if, as in the case of special education students, one is interested in showing how differently a student is performing from typically functioning students. Traditionally, “typical functioning” is defined in terms of the student’s chronological grade level. This means that converting RIT scores to standard scores is pretty straightforward. Grade-level means and standard deviation can be used from the NWEA norming study to accomplish this.
For example, an instructor needs to convert a grade four special education student’s spring RIT score of 189 in Math to a standard score. This formula would be used: (RIT – mean) / sd. When RIT is the student’s score, “mean” is the grade four spring mean (208.6) of the norm group, and “sd” is the standard deviation (14.23) of the spring grade four norm group. The standard score is then (189 – 208.6) / 14.23 = 1.38. The standard score (a.k.a., z score) means that the RIT score of 189 is 1.38 standard deviation, a negative number will be obtained when a student’s score is below the mean. This can be avoided by adopting a scaling factor (10, for example), multiplying the z score by this factor and then centering the scale around a sensible number (50, for example). In this case, resulting with (-1.38 * 10) + 50 = 36.2. The same basic process could be used for growth.
Using this formula assumes that the interest in the standard score is in standardizing the differences from a same-grade-level reference group mean. Standard scores show the distance from the mean at each point in time. If the standard score remains the same, the student is at the same distance from the mean. If the 4th grade student described above starts out below the mean and the standard score increases after a year, the student is performing closer to the 5th grade mean than he or she was to the 4th grade mean. Standard scores express only relation to the mean, not skill or performance. The standard scores are grade-level specific; so in terms of actual achievement, a 45 in grade 4 and a 45 in grade 5 would not mean the same thing. The grade (or group) specific reference for scale scores is one good reason for using RIT scores – they don’t depend on a grade level for their meaning.