GATE and CGPA

My colleague in IIT-M, Niket Kaisare, talks about GATE, GRE and the flight to US. He says, "If someone is incapable of securing more than a bare minimum threshold (in GATE), s/he is likely to struggle in the grad school." This was my point in my earlier post regarding GATE. If someone is unable to score 15% in GATE (50th percentile in chemical engineering paper), should he/she be interviewed for the Ph.D program at all? He remarks, "In fact, in the students I have encountered, there seems no correlation between GATE score and performance in the courses." I do not what was the data set and how good was the correlation. I had taken the CGPA of the masters students in the department for ten years and tried to correlate it against GATE percentile. The graph below is based on the CGPA of masters students during the period 2001-2006 (six year period) with their GATE percentile.

There was no correlation between CGPA and with students scoring above 95 percentile in GATE. However, when I divided the students into three groups: percentile less than 85, percentile between 85 and 95 and percentile above 95, the CGPA had a strong correlation with GATE percentile. For example, there was no student who had a CGPA of more than 5.5 but with a GATE percentile of less than 84.5. There was only one student who had a CGPA of more than 6.5 but with a GATE percentile of less than 94.5. Also, there was only one student who secured a CGPA of less than 5.5 but who had a GATE percentile of more than 95.