Final answer:
The shift from radio to television among households occurred during the early television era, as television sets rapidly became more common in American homes during the 1950s.
Step-by-step explanation:
As television grew more and more popular, households shifted their time from their radio set to television during the early television era. This period marked a transition when television sets became a common presence in American homes, rapidly increasing from being in 55% of homes in 1954 to 90% by 1960. The pivotal shift from radio to television mainly occurred because television combined the immediate and communal experience of radio with visual storytelling, thus captivating audiences in a new way. By the late 1950s, programs that were originally on radio began to move to television, further reinforcing this transfer of focus from radio to television among American households.