~ㅏ/ㅓ서 그런지 vs ~ㄴ지
1. 사고가 나서 그런지 교통이 복잡해요.
the speaker knows that there was an accident and the traffic is congested, but he/she is not sure if it’s because of that accident or not. there might be some other reason.
2. 사고가 났는지 교통이 복잡해요.
the speaker doesn’t know if there was an accident or not, but just guess that the traffic is congested so there might have been an accident.
By sentence 1 you can mean 2 but by sentence 2 you cannot mean 1.
In sentence 2, it’s definite that you don’t know if there was an accident or not.
사고가 난지 교통이 복잡해요(X)
we don’t use this sentence.
accident happens before traffic jam.
–>사고가 나서인지 교통이 복잡해요. you can say this.
1. 영희는 점심을 안 먹어서 그런지 벌써 배가 고프대요.
2. 영희는 점심을 안 먹었는지 벌써 배가 고프대요.
3. 영희는 점심을 안 먹어서인지 벌써 배가 고프대요.
Sentence 3 can mean both 1 and 2 by my intuition, but I’m not sure.
점심을 안 먹어서 그런지 벌써 배가 고파요.
You are hungry already, and you didn’t have lunch, so you think it’s probably because you skipped lunch.
점심을 안 먹었는지 벌써 배가 고파요.(x)
You are talking about yourself, so you should know if you had lunch or not. so this second sentence doesn’t make sense.
비가 와서 그런지 사람이 많이 없어요.
비가 왔는지 사람이 많이 없어요.
노란 색이 인기가 없어서 그런지 잘 안 팔려요.
노란 색이 인기가 없었는지 잘 안 팔려요. (x)
it doesn’t have any time gap.
노란 색이 인기가 없었는지 잘 안 팔렸어요.
노란 색이 인기가 없는지 잘 안 팔려요.
