6. The host computer system of claim 4 , wherein the comparison of the answer vector with the reference vector results in an answer score and the challenge result includes a challenge question, the quality control system further comprising: a challenge keyword score calculation module calculating a challenge keyword score based on the challenge keyword; a challenge question score calculation module calculating a challenge question score based on the challenge question; and a trigger score calculation module calculating a trigger score based on the comparison of the challenge keyword score with the challenge question score, the challenge answer-to-reference score calculation module calculating the challenge relevance score for the first engine based on the combination of the answer score and the trigger score.
7. The host computer system of claim 6 , the quality control system further comprising: an engine relevance score calculation module, wherein the challenge reference score for the first engine is calculated by the engine relevance score calculation module, the quality control system further comprising: an engine-level training module training the engine relevance score calculation module by: entering a plurality of training keywords into the first engine; receiving a training result page for each training keyword, the training result page being entered into the engine relevance score calculation module in association with a respective training keyword; and entering a training relevance score for each training results page into the engine relevance score, the training engine calculation module determining an engine-level parameter set based on the training keywords, training results pages and training relevance scores, the engine-level parameter set being used to calculate the challenge relevance score.