Leveraging Local Norms for Student Data: Your Top Questions Answered

Local norms are essential comparative scores calculated for specific student groups—whether it’s a district, a single school, a classroom, or demographic subgroups. By providing a more localized view of student performance, these scores aid in nuanced data interpretation and program placement decisions.

The DataManager platform and Riverside Scoring Service offer Local Percentile Ranks and Local Stanines for CogAT® and the Iowa Assessments™. For smaller subgroups or longitudinal data, you can also calculate these norms manually.

Below are answers to the most frequently asked questions regarding local norms.

How are local norms calculated?

Local norms are determined by finding the center (average) and the variability (standard deviation) of a specific score distribution. These two measures create a local distribution in which the highest scores reach the 99th percentile and the lowest reach the 1st percentile.

If you are using Excel to calculate local norms, you only need three functions:

• AVERAGE: To find the midpoint of the entire group
• STDEV: To express the variability of the scores.
• NORMDIST: To locate each individual student’s score within the calculated distribution using the average and standard deviation as inputs.

While manual Excel calculations will be very close to the results in DataManager, please note that DataManager uses a more complex calculation technique, so slight variations may occur.

What is the minimum number for using local norms?

There is no single minimum or maximum. The guiding principle is interpretational utility.

While local norms are most common in census testing (testing an entire grade level), they are incredibly useful for smaller subgroups:

• Classroom Level: Even with 15–20 students, local norms help teachers group students for projects based on ability or achievement.
• Gifted and Talented: Local norms help identify top performers among students who have already met referral criteria. Since these students often have similar Standard Age Scores (SAS), local norms reveal differences that national norms (where a SAS of 135 and 160 might both be in the 99th percentile) cannot capture.

How do I know when to use local norms?

Use local norms whenever you observe variability in a tested group and need a more sophisticated ranking than a simple "first to last" list.

• When to skip: If you only have 2–5 students, or if a larger group all achieved roughly the same score, local norms may not provide much additional insight.
• The Golden Rule: If the calculation isn't providing useful information for your placement or instructional decisions, you don't need to report it.

How many sets of local norms can I calculate?

A single student’s score can be used in multiple distributions. For example, a 2nd-grade student's score might be included in:

1. The district-wide 2nd-grade norms.
2. Their specific building norms.
3. A demographic subgroup (e.g., English Learners).
4. Their specific classroom norms.

This allows for multi-layered interpretation. A student who appears "average" at the district level might be a "high" performer within their specific program group, helping you tailor instruction more accurately.

Note on Longitudinal Data: If you are building a database to track norms over time, ensure you only compare years that used the same national norms (e.g., 2024 vs. 2017) to maintain data integrity.

About the Author

Dr. Joni Lakin, a Professor at The University of Alabama and co-author of the CogAT®, specializes in test validity and equitable assessment. A former postdoctoral fellow at ETS, she is dedicated to broadening participation in STEM and improving the identification of student potential within the public school system.