How do we know a study is enough for a phd - (Sep/14/2017 )

Hi, am writing proposal for my doctorate study. I wonder how phd study is different than Master's beside more aspects to research on (like how many more)?

How do we know the study is enough to secure a phd. Does it rely solely on our supervisor and faculty? 

Even back during my Master's, I often feel some students have way too much parameters/aspects to study on compared to mine. I manage to grad pretty early and sometimes I wonder if it's because of the fact that my supervisor is too kind.

You should ask your supervisor as it depends on him/her if it's enough or not. A quite good estimate might be publications...for a phd 2-3 peer-reviewed papers surely "secure" this or are even needed, depending on the doctoral regulations. This means (unfortunately) that you have to produce new, interesting results which are publishable...this is or can be a difference to master degree, where students sometimes just try out something (with unknown perhaps no results) or establish a technique and the results are anyway published earlier.

Anyway very few lucky dudes don't need to work more than a master student, if everything works perfect and the topics are so "sexy" that you can even publish a few results...

In a nutshell: not the quantity but more the quality is important for phd theses (though some supervisors want both).