This article discusses the relationship between the conditional growth index (CGI) and conditional growth percentile (CGP) found in many growth reports.
Introduction to conditional growthA short video is available in the MAP Help Center that helps introduce the concept of conditional growth. See What is conditional growth here: Growth Insights.
The conditional growth index (CGI) is an indicator of how much individual student growth deviates from the student growth norms. It is different from the growth index because the CGI indicates how many standard deviation units above or below the growth norm a student’s growth actually was, while the growth index simply indicates how many RIT points the student grew above or below the growth projections.
What is the conditional growth index?
Since the CGI is expressed in standard deviation units instead of RIT scores, it is a “standardized” metric. This means that you can use the CGI to compare students across grades, subject areas, and achievement levels.
A CGI of zero means a student showed gains that were equivalent to the growth norms. A positive CGI means a student’s growth was above the norm, while a negative CGI means a student’s growth was below the norm. A CGI above 1.0 indicates that a student's growth was greater than 1 standard deviation above the norm, which would represent a particularly high level of growth. By contrast, a CGI below -1.0 indicates that a student's growth was greater than 1 standard deviation below the norm. CGI between -1.0 and 1.0 represents the range within which the growth of the majority of similar students will fall.
How do I interpret a student’s CGI?
The CGI is particularly useful because it can be averaged. We also provide the conditional growth percentile, or CGP, for a more intuitive understanding of how a student grew compared to the NWEA norming group.
The conditional growth percentile, or CGP, is the student’s percentile rank for growth. If a student’s CGP is 50, this means that the student’s growth - compared to their growth projection - was greater than 50% of all students in the NWEA norm group.
What is the conditional growth percentile, and how do I interpret it?
Like the CGI, the CGP can be compared across grade levels and across subjects. Unlike the CGI, it cannot be averaged.
A student who has met their growth projection exactly will have a CGP of 50.
The CGI and the CGP are essentially the same information displayed in different ways. For example, if a student demonstrated growth equivalent to the norm, their CGI score would be 0 and their CGP would be 50. This is the case regardless of student grade, subject, or starting achievement level.
How are the CGI and CGP related? How do I calculate CGP from the CGI?
The CGI is a standardized metric, also known as a z-score. These scores are very commonly used in statistical analysis. The CGP is generally easier to understand, since percentiles are more commonly used in education.
Because both the CGI and CGP are readily available in NWEA reports, there is no need to calculate a student’s growth percentile (as was the case in previous years), as this metric will already be provided to you.
These metrics are found on the following reports:
Where can I find CGI and CGP on reports?
- Achievement Status and Growth Summary with Quadrant Graph
- Achievement Status and Growth (PDF or CSV)
- Comprehensive Data File
- Combined Data File
- Student Growth Summary (CGI and CGP based on the 2015 school norms, which indicates how grade levels compare to other similar grade levels, instead of how individual students compare to other similar students)
For more information, see: