An experiment was conducted to compare the mean reaction times to two types of
traffic signs: no left turn and left turn only. ten drivers were included in the
experiment. each driver was presented with 40 traffic signs - 20 no left turn and 20
left turn only - in random order. the mean reaction time to each type of sign was
recorded for each driver. so, for example, individual #1 reacted, on average, within
824 milliseconds to the no left turn and within 702 milliseconds to the left turn
only sign. the design of this experiment most closely resembles a: