一个问题，(想，要，想要)

Dear Robin

想 is still thinking, or the person is wish to do sth. 60% sure to do it

要 is a decition, he will do it

我想去公园 - I want to go to the park  (I'm thinking, mayby will go, but of course I wish to go)

我要去公园 - I want(or will) to go to the park  (I made the decition that I will go)

你要去吗？->do you want to go?    (you decided to go?)
你想去吗？->do you want to go?    (you wish to go?)

if you want to try tell it really strictly, it will be the difference like this, but depend on situation, both 想 and 要 could only mean "want", try to read more sentences and it will be helpful for you to get the language feeling ^_^

then:

想 要 and 想要  it could mean the same

Hopefully it will be helpful for you ^_^

Best/xiaolin

你想要去吗？=你想去吗？  Same meaning. Means: Do you want to go?

你要去吗？ A little difference. Means: Are you going to? (Maybe the person doesn't want to go but have to go.)

一个问题，(想，要，想要)

AII is right.想focus on mind a little more than behavior,要focus on behavior a little more than mind·，想要focus on both, anyway, they have no difference