英会話 feel English 23/5/24 L27 I guess.

ブログ記事から抜粋です。
英会話 feel English 23/5/24 L27 I guess.

I think と I guess は意味が似ていますが、ネイティブはどう使い分けているのでしょう?
(I think and I guess have similar meanings, how do native speakers distinguish between them?)

-Phrase Rank No.56
1). 「〜かなぁ」とあいまいに言うときの I guess
It’s lunchtime at the office.
-Dialogue
テルマとショーンはお昼休憩中。テルマはなんとなく元気がありません。
(Thelma and Shawn are on their lunch break. Thelma is somehow not feeling well.)
–
You guess?
What’s wrong?
family dog 実家の犬

–
How are you, Thelma?
Okay, I guess.
まあまあかなぁ。

Thelma, do you want to watch a movie?
Hmm. I’m pretty tired. I guess I’ll just go to bed.
Mmm, OK.

2). 根拠を持って推測するときの I guess
Emily and Olivia are carpooling to a barbecue with a bunch of friends. But one of them isn’t here yet
Dialogue ②
エミリーとオリビアは大勢の友達と車に分乗してバーベキューに行く予定ですが、サラがまだ現れません。
(Emily and Olivia are going to a barbeque with a group of friends, but Sarah still hasn’t shown up.)