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It is challenging to evaluate the results of GenAI applications because there are no expected results, only results from an acceptable range.  For summarization GenAI use cases, what are the most common evaluation metrics?

Hello Testers!  Below, I used LLM to summarize our discussion thread.  How would you rate the LLM summary ?
 

Evaluating GenAI summarization results is a complex task due to the lack of definitive "correct" answers. However, several common evaluation metrics and approaches are used to assess the quality and effectiveness of AI-generated summaries:

Automated Metrics

ROUGE (Recall-Oriented Understudy for Gisting Evaluation)

  • Measures overlap between generated and reference summaries using n-grams and sequences.
  • ROUGE-N focuses on exact matches, while ROUGE-L evaluates sequence similarity considering sentence structure.

BLEU (Bilingual Evaluation Understudy)

  • Originally designed for machine translation, it measures n-gram precision.
  • Useful for short texts but struggles with synonyms and paraphrasing.

BERTScore

  • Uses contextual embeddings to assess semantic similarity between generated and reference summaries.
  • Captures meaning better than surface-level metrics like ROUGE and BLEU.

METEOR

  • Considers synonyms and linguistic variations, offering better semantic evaluation than BLEU.

Human Evaluation

Human evaluation remains crucial for assessing subjective aspects of summaries:

  • Judges fluency, relevance, conciseness, and faithfulness.
  • Provides nuanced insights but can be time-consuming.

Other Evaluation Approaches

QuestEval

  • Assesses how well the summary answers questions derived from the source.
  • Useful for evaluating faithfulness and informativeness.

Factual Consistency Checks

  • Measures the accuracy of factual information retained from the source content.
  • Tools like QuestEval and FactCC can assist with this process.

Length-based Metrics

  • Evaluates whether the summary adheres to a desired length or compression ratio.

Novelty and Redundancy Analysis

  • Assesses whether the summary introduces unnecessary information or repeats content excessively.

Domain-specific Metrics

  • Customized metrics for specialized use cases (e.g., legal or medical summaries).

Frameworks and Tools

RAGAS Framework

  • Compares AI-generated summaries to ideal answers (Ground Truth).
  • Evaluates both retrieval and generation components of the model.
  • Key metrics: Answer Relevancy, Accuracy, Completeness, and Harmfulness.

NLGEval and EvalSumm

  • Frameworks to streamline evaluations across multiple metrics.

Best Practices

  • Combine multiple metrics for a balanced evaluation.
  • Use both automated metrics and human evaluation for comprehensive assessment.
  • Adjust metrics based on specific use cases and priorities (e.g., accuracy for legal documents, readability for blog summaries).
  • Implement regular health checks for LLM and data drift.
  • Consider user feedback for iterative improvement.

By utilizing a combination of these metrics and approaches, testers can effectively evaluate GenAI summarization outputs, ensuring both technical quality and user-centric value.


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