Tier 4 Dependents

Hi
I am a level 7 diploma student with dependents on 1 year tier-4 visa at private college.
I will complete my course in August 2015. from September 2015, I would like to extend my visa to do top-up 6 months final stage MBA (Dissertation) at University.

For 6 months, level 7 course, at HEI, Will I be eligible to gain dependents visa if I apply same time with main application from inside the UK?

To have a dependent you have to do a course that is longer than 12 months at an HEI.
So the answer is no.

To have a dependent you have to do a course that is longer than 12 months at an HEI.
So the answer is no.

Thank you for your reply, Mole

But T4 policy guidance says-

310. Dependants with existing permission wishing to extend their stay in the UK will be allowed to extend provided they apply at the same time as you apply to undertake a course of study that is longer than six months in duration.

Yip LONGER than 6 months. But not a six month course.