A network monitoring apparatus in a communications network detects TCP data flows (to at least one network-served end user) to provide corresponding detected data flows. This apparatus then measures data throughput to this (or these) end user(s) via the TCP data flows and during the TCP data flows and calculates an average effective data throughput to this end user. This calculation can be based, by one approach, upon use of time variables that represent the detected data flows (to effectively gamer a beginning-to-end view oft be various TCP data flows while avoiding inclusion of periods that represent no (or possibly only a little) volume in these regards as may be due to application idle time or end-user idle time while including periods that represent no (or possibly only a little) volume due to network buffering, device performance problems, and so forth).