1. A processor-based method for scoring a stimulus-response test for a test taker with a confidence value based on response-time measurement uncertainty, the method comprising: providing a testing unit, the testing unit comprising: a processor, an input device accessible to a test taker, an output device accessible to the test taker, an output data path connecting the processor to the output device, and an input data path connecting the input device to the processor; administering, with the testing unit, a stimulus-response test to the test-taker, administering the stimulus-response test comprising conducting a plurality of stimulus-response rounds, each of the plurality of stimulus-response rounds comprising: sending a stimulus signal from the processor to the output device via the output data path, the stimulus signal sent from the processor at a first time t 1 , the stimulus signal causing the output device to output a stimulus and prompting the test taker to respond to the stimulus at the input device; receiving a response signal from the input device at the processor via the input data path, the response signal received at the processor at a second time t 2 ; determining, with the processor, a round-trip signal time T RTS comprising a time interval between the first and second times; determining, with the processor, an estimated actual response time RT E to be a difference between the round trip signal time T RTS and a latency estimate L E , the latency estimate L E representing an estimate of a combination of: an output latency time between the first time t 1 and a time that the stimulus is output from the output device; and an input latency time between a time that the test taker responds to the stimulus at the input device and the second time t 2 ; determining, with the processor, one or more uncertainty values representing uncertainty associated with the plurality of estimated actual response times RT E ; determining, with the processor, a performance indicator for the test taker, the performance indicator based on the plurality of estimated actual response times RT E ; and determining, with the processor, a confidence value, the confidence value based on the one or more uncertainty values and representative of a confidence in the performance indicator.