Hello friend,
You have asked a very good question!
Generally, in interviews/selection processes, we find that a person who is able to "impress" the most or one who is very well prepared gets selected.
To avoid this, the interview is structured with very "specific questions" that are relevant to the company culture, company issues, and concerns.
These specific questions make the performance-based interview different from a normal interview.
These performance-based interview questions can improve the quality of selection. Also, such questions can be sent through email, and based on responses, suitable candidates can be short-listed.
This, of course, requires a lot of homework in understanding the job vacancy and very specific functional requirements so that proper questions can be prepared.
Please refer to a sample format enclosed. Here you would observe that we need to prepare specific questions for Performance Objectives of our company. For example, instead of going by the general assessment of the candidate's cost consciousness or cost reductions he has implemented earlier, we ask him, "We need to reduce our cost of the following 3 items - what approach would you follow?". Such specific questions will allow you to judge the person better.
Hope I have been able to answer you.
Regards,
Nishikant