1. An apparatus, including at least one processing device, for speech recognition, the apparatus comprising: a first confidence score calculator calculating, using the at least one processing device, a first confidence score using a ratio between a likelihood of a keyword model for feature vectors per frame of a speech signal and a likelihood of a Filler model for the feature vectors; a second confidence score calculator calculating a second confidence score based on a determined similarity between a Gaussian distribution trace of the keyword model per frame of the speech signal and a Gaussian distribution trace sample of a stored corresponding keyword of the keyword model; a determination module determining a confidence of a result using the keyword model in accordance with a determination of whether a position determined by the first and second confidence scores is included in a keyword area or in a non-keyword area on a confidence coordinate system including an axis of the first confidence score calculated by the first confidence score calculator using the at least one processing device and another axis of the second confidence score calculated by the second confidence score calculator based on the determined similarity, wherein the second confidence score calculator calculates the second confidence score using a weight value which given in accordance with a sub-word, a serial number, and an order of the mixed waveform probability distributions, and assigned in accordance with an arrangement order of the Gaussian distribution trace and the Gaussian distribution trace sample; and a controller identifying whether the first and second confidence scores are to be used to generate a reference function or to be used to recognize the speech signal, wherein the first and second confidence scores are transmitted to the determination module when the controller identifies that the first and second confidence scores are to be used to recognize the speech signal, and wherein at least one of a position and form of the generated reference function is updated based on the speech signal.
7. The apparatus of claim 1 , further comprising a reference function generator generating the reference function, which is a boundary serving as a standard of judgment as to the confidence score in accordance with the position, wherein the controller transmits the first and second confidence scores to the reference function generator when the controller identifies the first and second confidence scores are to be used to generate the reference function.