Conditional growth percentile

Document created by Community User on Jul 29, 2016Last modified by Community User on Jun 6, 2017
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Question
What is the conditional growth percentile (CGP)?

Answer
The conditional growth percentile, or CGP, is a student’s percentile rank for growth. If a student’s CGP is 50, this means that the student’s growth was greater than 50 percent of similar students in the NWEA norm group. Students are similar with regard to starting achievement level, grade, subject area, and number of instructional weeks between test events.

A student who demonstrated growth equivalent to that of similar students (that is, equal to the student growth norms) will have a CGP of 50. Growth greater than the norm would result in a percentile rank higher than the 50th percentile, and growth less than the norm would result in a percentile rank lower than the 50th percentile. CGPs range from the 1st to 99th percentile.

CGPs can be compared across grade levels and across subjects, but should not be averaged. This means that, if you have two students who have CGPs of 25 and 75, you can say that the student with a CGP of 75 grew more compared to their norm group than the student with a CGP of 25. However, it would not be valid to say this group of students, on average, has a CGP of 50.

 
How can you calculate the CGP?

Because both the conditional growth index (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. This metric will already be provided to you.

The CGP is found on the following reports below:
  • Achievement Status and Growth Report
  • Student Growth Summary Report
  • Comprehensive Data File and Combined Data File

 
What is the relationship between CGI and CGP?

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, his or her CGI score would be 0 and his or her CGP would be 50. This is the case regardless of student grade, subject, or starting achievement level.

The CGI is a standardized metric, also known as a z-score. These scores are very commonly used in statistical analysis. However, the CGP can be easier to understand than the CGI, since percentiles are more commonly used in education.

 
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