GRAMMAR DETAIL

〜ということは

the fact that ... means

Draws a conclusion about a situation from the fact established beforehand.

Examples

電気が消えているということは、店はもう閉まったのだろう。

The fact that the lights are off means the store has probably already closed.

彼が来ないということは、予定が変わったのかもしれない。

The fact that he is not coming may mean that the plans have changed.

Structure: After a clause, ということは takes its content as a fact to serve as the topic for an inference.
Basic usage: 彼が来ないということは、予定が変わったのかもしれない。 expresses an inference about a possible change of plans based on his not coming.

Certainty of evidence versus conclusion
- Even if 電気が消えている is established, 店はもう閉まったのだろう remains a conjecture. ということは does not itself make the conclusion certain; the qualifications in だろう and かもしれない remain.