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Scoring Service API
Assigns an ability estimate to an assessment-taker in the form of a Lexile Reading, El Sistema Reading, or Quantile measure.
About Scoring Service REST API
Reporting Scoring Service Measures
The Scoring Service API uses the Lexile® and Quantile® frameworks to calculate student ability measures. The API now returns two measure fields in every response: a research measure and a display-ready measure with all required formatting rules already applied.

APIs
- Scoring Service API
  Assigns an ability estimate to an assessment-taker in the form of a Lexile Reading, El Sistema Reading, or Quantile measure.
  - About Scoring Service REST API
    - Service Level Agreement for Scoring Service API
    - High Availability
      High Availability (HA) of MetaMetrics® Services.
    - Bayesian Scoring Theoretical Foundations
      Everyone has heard the maxim “the best predictor of future behavior is past behavior.” Bayesian Scoring is a statistical approach for predicting a student’s test score by incorporating both the student’s prior test scores and the uncertainty associated with all measures into an adjustment to the current score. The more confident we are about the prior information, the smaller is the standard deviation of the prior information (Yen and Fitzpatrick, 2006). The result is that the adjusted score is a more accurate measure of the student’s “true” ability level. The MetaMetrics Scoring Service API is a scoring technology that updates student ability measures – Lexile or Quantile measures. Calculations are made by incorporating historical student performance data and current test experiences to estimate new, more refined ability estimates.
    - Reporting Scoring Service Measures
      The Scoring Service API uses the Lexile® and Quantile® frameworks to calculate student ability measures. The API now returns two measure fields in every response: a research measure and a display-ready measure with all required formatting rules already applied.
    - Scoring Service Response Codes
    - Scoring Service REST API — Response Fields Reference
      This article describes the fields returned in all Scoring Service API responses. These fields are consistent across both Standard Scoring and Bayes Scoring endpoints.
    - Scoring Service REST API FAQ
      The process of scoring student assessments and reporting results has evolved greatly over the years. From teachers sitting with paper-based answer sheets to bubble-sheets fed through a machine that produces a percent correct, technology has helped to enhance the process of scoring tests. While percent correct on an assessment can be valuable, many assessments benefit from reporting an estimate of the underlying student ability in an educational construct. These ability estimates provide indicators of status and can be used to monitor growth over time.
  - API Calls
  - Service Level Agreement for Scoring Service API
- Lexile Text Analyzer API
  Analyzes text to produce Lexile text measures on custom content.
- Titles API
  Access more than 470,000 hardcover, e-books, paperback, trade and other titles.
- Forecasting API
  Forecast an individual student or group performance on an upcoming assessment.
- Growth Planner API
  Plot a student's projected growth using Lexile or Quantile measures.
- Oral Reading API
  Measures a student's oral reading ability and the oral readability of text on the same scale.
- PowerV API
  Create and access vocabulary lists for over thousands of titles with the Titles Database.
- Career Database APIs
  Identify a career’s reading and math demands in Lexile and Quantile metrics for goal setting and career preparedness.

Reporting Scoring Service Measures

The Scoring Service API uses the Lexile® and Quantile® frameworks to calculate student ability measures. The API now returns two measure fields in every response: a research measure and a display-ready measure with all required formatting rules already applied.

Note: This page has been updated to reflect the introduction of the abilityDisplay field. Partners no longer need to apply business rules manually. See details below.

For detailed information about each framework represented in the Scoring Service API, see:

The Two Measure Fields

Every Scoring Service API response returns both of the following fields:


Field	Type	Description	When to Use
`ability`	number	The research measure, without any business rules or formatting rules applied.	Research, institutional reporting, analysis, or as input to Bayesian scoring calls (priorAbility).
`abilityDisplay`	string	A display-ready measure with all required business rules automatically applied, including rounding, caps, BR/EM conversion, and framework label.	Displaying results to teachers, parents, or students in any user interface or report.

Note: Partners previously applying business rules to the ability field should transition to using abilityDisplay for all display purposes. The ability field remains available and unchanged for use cases that require the research value.

What abilityDisplay Does Automatically

The following business rules are applied automatically before the abilityDisplay value is returned. Partners no longer need to implement these rules in their own systems.


Rule	Description	Example
Rounding	The measure is rounded to the nearest 5.	572 → 570, 577 → 575
Capping	Upper and lower scale caps are applied automatically. Reported scores will not exceed the maximum or fall below the minimum for the framework.	A score above the scale cap is returned at the cap value.
Negative conversion (Lexile)	Negative Lexile measures are expressed as BR (Beginning Reader).	-200 → BR200L
Negative conversion (Quantile)	Negative Quantile measures are expressed as EM (Emerging Mathematician).	-200 → EM200Q
Spanish Lexile	Any Spanish Lexile measure below 0 is converted to a generic BR rating.	Negative value → BR
Framework label	The appropriate label is appended: L for Lexile, Q for Quantile.	570 → 570L or 570Q