In a question-response practice, the question is "你暑假要去旅游吗"? Why is the right response "我还没决定", not "我还没打算"?
In the narrow sense of a q&a practice, I would say that by saying ‘我还没打算’ you are not answering the question if you want／are going to travel (你暑假要去旅游吗), while 我还没决定 (I haven't made up my mind yet) is a very clean answer.
我还没打算 is like 'I didn't plan (the trip) yet'. Also, compare this answer to something like: '暑假我没有计划' (I have no plans for the summer holidays).
I hope this helps!
“我还没打算“ literally means "I do not have intentions yet."
“我还没决定“ literally means "I have not decided yet."
When someone asks you if you are going on a trip for vacation, and you don't actually know if you are going or not, both are logically true. However pragmatically: The former means that you are currently not planning to do so, though the situation may change in the future. In that, you are expressing something like "Not for now, though I may." in which you mean that you have decided not to go on a trip given the current circumstances, although this decision may change. The latter means that you have no specific answer to the question. In that, you are expressing something like "Maybe, maybe not." in which each situation has an unknown probability of happening, and you have no decision at all.
In fact both answers are correct and practical. However, 打算 as a verb means "to plan", so the sentence may as well be interpreted as "I have not planned yet.", which can be further extended to "I have not planned on trips in my holidays yet.", which is not what you mean and doesn't sound natural (I believe that this is the reason it is wrong) since 打算 as a verb is most often accompanied by an action you are (perhaps not) planning to do. To make it clear that 打算 is a noun, simply add a determiner: "this". “我还没有这个打算“ would more precisely mean that "I do not have these (such) intentions yet." Also, since it means that the situation is temporary, it may sometimes sound more natural if you add "temporarily": “我暂时还没有这个打算“.
You should be able to see the difference between 打算 and 决定 better with the following question:
What do you plan to do during the holidays.
I haven't make any plans.
I plan to travel, but haven't decide where to go.
In your practice question, because 旅游 has been proposed by the asker as a specific plan for the holiday, 决定 would be an appropriate answer if the answerer has thought about it but not come to a decision. It is not wrong to use 打算 if the answerer has not even entertained that idea of travelling.
In any case, without further context, there is no way to tell whether the answerer has considered how to spend his holiday to know which would be the "correct" response.
I don't think "我还没打算" is absolutely wrong; both responses are fine.
"我还没打算" does sound a little unnatural/ambiguous because the question is suggesting a plan and a spot-on response should acknowledge it by saying "I'll consider" or "I have decided" or "that's not the plan".
By responding with "我还没打算" (I don't have a plan yet), it is unclear whether it means "I don't have a plan for the summer yet, so travel is an option" or "I don't have a plan for travel yet". Either way it's not a straight-forward answer to the question.
But you can say "我还没有这样的打算" (I don't have such plan yet), then it becomes clear - "I don't have plan to travel yet". This response sounds natural and is actually commonly heard.
On the other hand, saying "我还没决定" implies "I have already thought about travel before you ask, but have not decided yet" which is usually used in a follow-up conversation. The semantic is also clear and answer the question well.
Based on the conversation you provided, I guess that when the guy in the exercise asks you 你暑假要去旅游吗, she/he probably knows that you have already planned the trip, or already had the idea in your mind. So she/he is asking for your final decision, therefore 决定 is used.
However, in my opinion, 我还没打算 should also be correct, where you could say 还没这个打算 as well.
Actually as a Chinese, I think "我还没打算" is OK in practical use. Then I asked 5 of my classmates and they think the same .
However, they also mentioned there might be a little difference that "我还没打算" means "I haven't think of it (at all)", while "我还没决定" shows that you have thought of it but haven't decided whether to travel.
Let me summarize so it can show whether I really understand. (If not, please correct me.)
- In practical use (real life), both are fine. But "我还没打算" might be ambiguous, since different listeners might interpret it differently.
- "我还没决定" is more direct to answer the question. In a test when both exist, "我还没决定" is preferred as "correct" response.
Thank you very much for all your help! 谢谢。