1. A system for providing hiring recommendations of agents within a call center, comprising: a handset to collect a voice sample from a candidate agent; a spectrum analyzer device to determine within the voice sample voice characteristics comprising at least one of pitch, range of resonance frequencies of vowel, average resonance frequency of particular vowels, spectral tilt, breathiness, creakiness, nasality, speed of words, pause duration and intonation; and a speech recognition server comprising a central processing unit, memory, an input port that receives the voice sample from the handset, and an output port, wherein the central processing unit is configured to: compare the voice characteristics from the voice sample with at least one graph comprising voice characteristics for two or more populations of a trait, which are each represented by a curve; assign a score to the candidate agent by identifying at least a portion of the voice characteristics from the voice sample on the graph based on the comparison, assigning a numerical value to each identified voice characteristic from the voice sample based on the comparison, and summing the numerical values for the identified voice characteristics as the score; identify one of the populations to which the candidate agent belongs for that trait based on the assigned score; and provide a recommendation for hire for the candidate agent based on the assigned score and the identified population.