This measures the factual consistency of the generated answer against the given context. It is calculated from answer and retrieved context. The answer is scaled to (0,1) range. Higher the better.

The generated answer is regarded as faithful if all the claims that are made in the answer can be inferred from the given context. To calculate this a set of claims from the generated answer is first identified. Then each one of these claims are cross checked with given context to determine if it can be inferred from given context or not. The faithfulness score is given by divided by

(1)\[\text{Faithfulness score} = {|\text{Number of claims in the generated answer that can be inferred from given context}| \over |\text{Total number of claims in the generated answer}|}\]


Question: Where and when was Einstein born?

Context: Albert Einstein (born 14 March 1879) was a German-born theoretical physicist, widely held to be one of the greatest and most influential scientists of all time

High faithfulness answer: Einstein was born in Germany on 14th March 1879.

Low faithfulness answer: Einstein was born in Germany on 20th March 1879.


from datasets import Dataset 
from ragas.metrics import faithfulness
from ragas import evaluate

data_samples = {
    'question': ['When was the first super bowl?', 'Who won the most super bowls?'],
    'answer': ['The first superbowl was held on Jan 15, 1967', 'The most super bowls have been won by The New England Patriots'],
    'contexts' : [['The First AFL–NFL World Championship Game was an American football game played on January 15, 1967, at the Los Angeles Memorial Coliseum in Los Angeles,'], 
    ['The Green Bay Packers...Green Bay, Wisconsin.','The Packers compete...Football Conference']],
dataset = Dataset.from_dict(data_samples)
score = evaluate(dataset,metrics=[faithfulness])


Let’s examine how faithfulness was calculated using the low faithfulness answer:

  • Step 1: Break the generated answer into individual statements.

    • Statements:

      • Statement 1: “Einstein was born in Germany.”

      • Statement 2: “Einstein was born on 20th March 1879.”

  • Step 2: For each of the generated statements, verify if it can be inferred from the given context.

    • Statement 1: Yes

    • Statement 2: No

  • Step 3: Use the formula depicted above to calculate faithfulness.

    \[\text{Faithfulness} = { \text{1} \over \text{2} } = 0.5\]