Academics · Subject Resources

See where a score sits on the curve.

Evaluation reports speak in standard scores, scaled scores, T-scores and percentiles. Type the numbers from the report and see each one on the bell curve, converted to every other scale and written out in plain words.

Plot a score What you get

The visualizer

The worked example is a made-up report with nine scores. Tap a score to put it on the curve, or drag the slider and watch the percentile move. Nothing you type leaves this browser.

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What you get

Academics · Subject ResourcesFree

What you finish with: Every score from a report placed on the normal curve: its percentile rank, the same score as a standard score, scaled score, T-score, z-score, stanine and NCE, the report’s range drawn as a band, a plain-language sentence for each, one chart of the whole report, and a printable summary with questions for the meeting.
Who it is for: Parents and guardians reading a school or private evaluation, students old enough to read their own results, and the tutors and teachers who sit beside families at eligibility and IEP meetings.
Format: Browser tool. Works on a phone or computer. Print or save as PDF, a .csv spreadsheet, and a file to move the scores between devices.
Access: Free. No account and no sign-in. Scores stay in this browser; nothing is sent to Caveat. The page never asks for a name.
Where it lives: The Subject Resources space in Caveat Academics.
Support: Questions, a correction or a request: team@caveatacademic.com.

One curve, five rulers. Every scale on a report is a different set of numbers for the same place on this curve.

How to use it

Find the score tables in the report. For each score, note the scale it uses: most composite scores are standard scores (average 100), many subtests are scaled scores (average 10) and many rating scales use T-scores (average 50).
Type each score and, if the report prints one, its range or confidence interval.
Tap a score to put it on the curve. Read the sentence under it, then drag the slider to see how fast percentiles change near the middle and how slowly at the ends.
Read the chart of every score. Where two ranges overlap, the difference may be measurement error.
Print the summary and bring it, with your questions, to the meeting.

Plot a score

What the numbers mean

Every scale on this page is a different ruler laid along the same normal curve.

The scales

Standard score: average 100, standard deviation 15. Used for composite and index scores on most cognitive and achievement tests.
Scaled score: average 10, standard deviation 3. Used for single subtests.
T-score: average 50, standard deviation 10. Common on behavior and attention rating scales, where a higher score usually means more concerns.
z-score: the number of standard deviations above or below the average.
Percentile rank: the percent of same-age students in the norm group who scored the same or lower. The 16th percentile is one standard deviation below the average; the 84th is one above.
Stanine: nine bands with 5 in the middle. All but the first and last are half a standard deviation wide. NCE: average 50, standard deviation 21.06, so that 1, 50 and 99 match those percentiles.

What to keep in mind

A score is an estimate. The range printed beside it (often a 90% or 95% confidence interval) is the honest version of the number.
Labels such as Average or Below Average are set by each test. Many tests call 90 to 109 Average; others use 85 to 115. Use the label your report prints, and ask which system it follows.
Percentiles bunch up in the middle. Going from 100 to 105 moves a score from the 50th to the 63rd percentile; going from 65 to 70 moves it from the 1st to the 2nd.
This page converts with the normal curve. A report’s percentiles come from the test’s own norm tables and can differ by a point or two, mostly at the far ends. When they differ, the report is right.
Age and grade equivalents are not on this curve and are easy to misread. Ask for the standard score instead.
No single score decides anything. Federal special education rules require a team to use a variety of measures.

The worked example, checked when the page is built. The report is made up. Working memory, a standard score of 85, is exactly one standard deviation below 100, so it sits at the 16th percentile and equals a scaled score of 7, a T-score of 40, stanine 3 and an NCE of 29. Its range of 79 to 93 runs from the 8th to the 32nd percentile. Word reading at 78 is at the 7th percentile and verbal reasoning at 104 is at the 61st; their ranges, 74 to 82 and 97 to 110, do not overlap. The teacher rating of T 68 is at the 96th percentile, and on that scale higher means more concerns.

Sources

American Educational Research Association, American Psychological Association and National Council on Measurement in Education, Standards for Educational and Psychological Testing (2014): scales, norms, score interpretation and the standard error of measurement.
National Institute of Standards and Technology, NIST/SEMATECH e-Handbook of Statistical Methods, section 1.3.6.6.1, "Normal Distribution" (itl.nist.gov/div898/handbook).
George Marsaglia, "Evaluating the Normal Distribution," Journal of Statistical Software 11, no. 4 (2004): the series this page uses for the area under the curve, checked against Python’s statistics library when the page is built.
Individuals with Disabilities Education Act regulations, 34 CFR 300.304(b): an evaluation uses a variety of assessment tools and strategies and no single measure as the sole criterion.

This page explains what score scales mean. It does not interpret a child’s evaluation, decide eligibility or diagnose anything; the evaluator and the school team do that with far more information than a number. The example report is made up, and its skill names are generic, not taken from any published test. Support: team@caveatacademic.com.