Final answer:
To spot an impaired driver, one should look for inconsistent signaling as a key indicator; attending to personal hygiene or talking on a cellular phone may cause distraction but are not direct signs of impairment.
Step-by-step explanation:
To spot an impaired driver, one must look for behavior that may indicate a lack of attention or inconsistency in driving patterns. Inconsistent signaling, such as turning on the signal but not turning or signaling in a direction opposite to the actual maneuver, can be a sign of impaired driving. This is not to be confused with attending to personal hygiene or talking on a cellular phone, which, while potentially distracting, are not direct indicators of impairment from alcohol or drugs.
Regarding the provided information, it seems like the question might involve a statistical analysis related to cell phone use while driving and violations. However, this does not directly relate to the act of spotting an impaired driver in real-time. When considering the observer effect, it is crucial to monitor drivers when they are unaware to get an accurate measure of their typical behaviors. Using a cell phone can be particularly distracting and may contribute to poor driving behaviors, but it is the inconsistent signaling that is the key indicator of impairment as per the question.