A C172 pilot reported they taxied onto the runway to depart from a non towered airport causing an aircraft on short final to go around.

Narrative

On checking for traffic while at the hold short line; I perceived none; proceeded onto the runway; inadvertently forcing another aircraft to go around. Taxiing to and during the run-up checklist; I observed and heard radio calls from two aircraft in the pattern. They appeared to be conducting touch 'n go's in left closed traffic. After completing the run-up checklist I started toward the hold short line. As I did so; I heard one more radio call from an aircraft in the vicinity; but did not process where or what they were doing.Pausing at the hold short line; I listened and waited several seconds for the appearance of any aircraft that might be on turning base or on final.Hearing no further call; and seeing no traffic on base or final; I assumed the nearest aircraft were still on the downwind leg. I called my departure and proceeded onto the active runway. As I did so; the same voice as the last call calmly announced they were going around. I asked if I had cut them off; and they confirmed that I had (to which I apologized). In retrospect; I realized their earlier call had been a simulated engine out; and they had been turning toward the runway at or inside the runway numbers; coming from behind and passing almost directly overhead - the reason I did not see them. Obviously; my assumption was faulty. In an engine out simulation; I should not have assumed the pilot would fly a regular pattern. Not knowing exactly where they were at; I could have checked via the radio. I should have; and won't hesitate to do so in the future. Also; Aircraft in this area usually have ADS-B Out as it is required in the nearby Mode C veil. I use navigation software that can connect to ADS-B In; but I don't currently have one. It would be a good investment.