Conditional growth index: Definition and calculation

Document created by Community User on Jul 29, 2016Last modified by Community User on Apr 17, 2019
Version 318Show Document
Introduction
What is the conditional growth index? How is it calculated?

Information

What is CGI?

The conditional growth index (CGI) is a normative growth metric. It is a standardized measure of observed student or school growth compared to the 2015 NWEA student or school growth norms. These growth norms indicate median growth levels for students or schools based on their grade, starting RIT score, the subject in which they tested, and the amount of instructional time between two test events.

Also known as a z-score, the CGI expresses student growth in standard deviation units above or below the growth norms. A CGI score of zero indicates a student showed the same amount of growth as the growth norms. Positive CGI scores indicate that a student’s growth exceeded the growth norms, whereas negative CGI scores indicate that a student's growth was less than the growth norms. A CGI score of 1.0 means a student's growth is one standard deviation above the growth norm; conversely, a CGI score of -1.0 means a student’s growth is one standard deviation below the growth norm. The CGI allows for growth comparisons to be made between students of differing achievement levels, and across different grades and subject areas.

How is CGI calculated?

MAP Growth reports calculate the CGI for you. It is available on the reports shown below:
NWEA also provides growth calculators you can use to calculate the CGI:

Can I calculate the CGI manually?

You can roughly calculate a student or school's CGI manually. The CGI displayed on reports or in the calculator is more precise. This is because the growth data displayed in the reports is rounded to the nearest integer, and the standard deviation for growth in the 2015 Norms study does not take into account your customized weeks of instruction. Therefore, the CGI you calculate will likely be slightly different, and less precise, than the CGI displayed on reports. NWEA recommends using MAP Growth reports or the Achievement Status and Growth or School Norms calculators.

As with other z-scores, the formula for calculating the CGI manually is Growth index / Standard deviation for growth. The formula for growth index is Observed growth - Projected growth.

These values are found on the following reports that are listed below: