MARIN FANJOY-LABRENZ

ProjectLexical Diversity

Client
English Literacy Platform
RoleInstructional Designer
OverviewDuring this project, I conducted research into computational metrics for evaluating lexical diversity and sentence complexity. New scoring categories, along with the introduction of subscores, enhanced our scoring accuracy and allowed us to provide students with more meaningful insights into their English proficiency.
Year2023

























PROBLEM
 In our assessments, students write paragraphs of ±30-60 words in response to a prompt. Initially, we scored writing samples on a 0-20 scale in five categories:

  1. Holistic Quality
  2. Genre Elements
  3. Correct Word Sequence
  4. Readability
  5. Complex Words

While categories 1-3 were accurately scored by human raters, categories 4-5 used computational methods that introduced significant inaccuracies. Readability calculations using the Flesch-Kincaid formula and complex word percentages produced unreliable results for short text samples.

Our research aimed to identify and integrate alternative metrics to assess the readability and sophistication of a writing sample. We also researched options for scoring scales that would allow students to see more growth on their assessment reports.





RESEARCH

Our objective for this research was to find metrics to assess a student's

  • Lexical Profile: Vocabulary usage, variety, and accuracy
  • Sentence Variety and Accuracy: The ability to construct clear, varied sentence structures

Additionally, metrics must be:

  • Easy and quick to determine using rubrics or computational methods
  • Less susceptible to innacuracies due to short text length





















LEXICAL PROFILE (LP)After extensive research into lexical diversity measures, I selected the Measure of Textual Lexical Diversity (MTLD) for its resistance to text length variations as one half of the LP score. For lexical sophistication, I averaged two distinct metrics, the Academic Word List (AWL) and the English Vocabulary Profile (EVP).  

Lexical Profile = Lexical Diversity + Lexical Sophistication

                            = MTLD + AVG(AWL, EVP)




LEXICAL DIVERSITY
Chosen metric:

Measure of Textual Lexical Diversity (MTLD)MTLD Characteristics

  • Typically ranges from 0-100, where lower numbers indicate less lexical diversity
  • Evaluates texts sequentially, measures average words read before type-token ratio falls below 0.72
  • Less sensitive to text length because it maintains consistent factor size
  • Retrieved using Text Inspector
  • Rounded to nearest whole number
  • Translated to 0-9 scale using a piecewise function







LEXICAL SOPHISTICATIONChosen metrics:

Academic Word List (AWL) & English Vocabulary Profile (EVP)AWL Characteristics

  • Percentage of words from Averil Coxhead's academic word families
  • Retrieved using Text Inspector
  • Rounded to nearest tenth
  • Typical range: 0-10%
  • Translated to 0-9 scale using a piecewise function

EVP Characteristics

  • Percentage of unique words at B1 CEFR level
  • Uses UK vocabulary list
  • Retrieved using Text Inspector
  • Rounded to nearest tenth
  • Typical range: 0-20%
  • Translated to 0-9 scale using a piecewise function




SENTENCE VARIETY & ACCURACY (SVA)Colleagues simultaneously developed a 0-9 rubric that evaluated:

  • Clarity of sentence structures
  • Variety of clause arrangements
  • Effectiveness of sentence structures in conveying meaning
  • Sentence complexity and intentional communication
















    IMPACT ON DESIGN
    We implemented several key changes to make our scoring scale and reports more student-friendly:

    Scoring Scale:
    • Version 1: Categories scored 0-4, totaling 20 possible points
    • Version 2: Categories scored 0-18, totaling 90 possible points

    Contextualization:
    • Version 1: Scores directly compared to CEFR
    • Version 2: Replaced direct CEFR correlation with standardized cateogires specific to the platform's curriculum

    Subscores:
    • Version 1: Feedback based on total score
    • Version 2: Three subscores displayed numerically, allowing performance-based customization





    RESULTSBy implementing advanced linguistic analysis techniques like the Measure of Textual Lexical Diversity (MTLD) and developing a comprehensive rubric, we significantly improved the precision of our English proficiency assessments. The new scoring system allowed us to provide students with more detailed feedback about their writing skills and linguistic development.