Hi there, 

Let me try to help, but please bear in mind that the very specifics of the interviewing process might have some variability between offices. So do take this as indicative. 
 

1. Since this is the final round will the decision be made only by the final interviewer?

Typically no. If part of a structured interview round (aka more candidates at the same level applying in a recruiting window), then all interviewees that passed previous rounds will be re-assessed together and often compared to each other. 

Exception to this is if you apply to a more specialized / senior, where there is not a pool of candidates per se. 

2. What is the margin of error? If I make a single mistake will I get rejected

Also typically no. It will depend greatly on the error. To illustrate: if you make 1 math error, but otherwise had an excellent interview, this would not normally get you rejected. There are probably some bad mistakes out there that would get you rejected, but I guess saying something really stupid would qualify there - so I doubt that will be the case. 

Interviews are hard enough, don't put additional pressure on yourself! 

3. Will the difficulty of the case be higher than the rounds before?

Somewhat. Typically, as your interviewers get more senior, their cases are more “out there” or atypical. So you could get a case that seems easier than the previous ones, or one that seems very unconventional (for good or bad). As a rule of thumb, the more senior someone is, the more they would appreciate well summarized insights! 

4. Will they take special attention into the previous rounds and what were the suggested improvement points? (i.e if I am not able to improve a lot in this - only 3 days until interview from previous one)

I think yes. Sorry for that news. In consulting, feedback is taken very seriously - it is a big investment to provide good quality feedback, so once shared, there is an expectation to improve. 

That being said, I think it is fine to show at least some improvement (hard to say what is a lot or a little), also calibrated with time between interviews. 

Hopefully this is somewhat doable, given you did pass the previous rounds - so this would indicate there are maybe things to rather be aware of than completely change your approach for. 

I hope this helps and best of luck for your upcoming round! 

Ariadna 

Dear candidate,

congratulations and great questions. Wonderful you are so far.

1. Since this is the final round will the decision be made only by the final interviewer?

The final interviewer can most of the time directly give you a decision in the interview. However they may or may not do this, may keep you waiting, too. In many cases a decision is communiated

2. What is the margin of error? If I make a single mistake will I get rejected. No. there are many mistakes you can make however dont make one on purpose, for example think of the interview to deliver 100% perfection, great arguments for why you should be hired and you will succeed. Think of selling your plus points, what is unique about your learning curve and experience? If you can what huge value to the firm do you offer?

3. Will the difficulty of the case be higher than the rounds before?

often are. practise extra and see structuring, communicating clearly your approaches and assumptions, and summarizing so whats, if this is the style , drive case proactively. Be there to shine with your experience know how and your innovative susgestions.

4. Will they take special attention into the previous rounds and what were the suggested improvement points? (i.e if I am not able to improve a lot in this - only 3 days until interview from previous one). This round really matters. Focus on this round and deliver stellar performance. You certainly can. 

Best wishes.