The selection of candidates for admission to the 2013-15 batch of the PGP at IIM Ahmedabad is a two-step process.
In the first step, candidates are short-listed for personal interviews from among candidates who have a valid CAT/GMAT score* who have applied for the programme and who satisfy the eligibility criteria for the programme. An overseas category candidate who applies with a GMAT score instead of a CAT score should have a total scaled score of at least 700.

A candidate's prior academic record is also used in the short-listing process.

Short listing Criterion:
70% weightage is given to the CAT/GMAT score and 30% weightage is given to the Application Rating Score.

Application Rating (AR): 2013-15

• Percentages for incomplete Bachelor’s Degree Applicants are based on their available marks.
• Only those with completed Master’s Degree is considered. For those with more than one completed Master’s Degree the highest percentage of marks obtained is to be used.
• For those candidates having cleared CA/ICWAI without having Bachelor’s Degree, their average of inter and final levels marks will be treated as Bachelor’s degree marks.
• For computing the application rating, all subjects that appear in the mark-sheet of 10th and 12th Std. exams. will be considered irrespective of whether the Board/University considers them for calculating the percentage. For bachelor’s degree, marks obtained in all the subjects as mentioned in the mark-sheet in all the years will be taken into account.If you have a 5 year integrated Master's degree, percentage of marks obtained in the first 3 years will be considered as bachelor’s degree percentage and the percentage of marks for the remaining 2 years as Master's degree percentage. If you are in the final year of 5 year integrated Master's degree, the marks obtained in the first 3 years will be considered as bachelor’s degree Not Completed percentage.

Application Rating Score: (AxBxC)+D+E

In the second step, after the completion of personal interviews of all candidates short-listed in the first step, candidates for admission to the 2013-15 batch of the PGP at IIM Ahmedabad are selected from among the candidates who have attended the personal interviews. In preparing this list, apart from performance in the personal interview, the CAT/GMAT score*, academic performance and achievements, extra-curricular activities, and post-degree work experience are also taken into consideration.

Selection Criterion:
70% weightage is given to Personal Interview Score and 30% weightage is given to the CAT/GMAT Score. (Note: The Personal Interview Score is based on the following: performance in the personal interview, academic performance and achievements, extra-curricular activities and post-degree work experience.) 

For more details check out the information on their official website. 
Selection criteria for year 2012-14 (CAT-2011)