Final answer:
Throughput is the best metric for measuring the raw performance and actual data transfer speed of a network. It provides a realistic picture of network performance as experienced by the user, unlike speed, relative jitter, or availability.
Step-by-step explanation:
The best raw performance metric to determine the speed of a network for mobile users is throughput. Throughput measures the actual amount of data successfully transferred over the network in a given amount of time, typically measured in bits per second (bps), kilobits per second (Kbps), megabits per second (Mbps), or gigabits per second (Gbps). It reflects the network's ability to handle traffic and is an effective indicator of the network's performance from the user's perspective.
Other metrics like speed can be ambiguous because it often refers to the theoretical maximum of a connection and not the practical speeds experienced by users. Relative jitter measures the variation in packet arrival times, which is important for real-time applications but does not directly equate to network speed. Availability measures the time a system or component is operational and accessible, but again does not provide a measure of how fast the data is moving through the network.