Is this fishing for some sort of awestruck response, by any chance? I only ask after seeing your "How many pressups can you do in two minutes" thread- I'm just waiting for you to pop back on there to comment about how much more than anyone else you can do.
Some people on this site will never run that distance at all, let alone in half an hour. On the other hand, there are people on this site that would be disappointed if they could only run that distance in 29 minutes.
A mile and a half should be done in 10 mins, therefor half a mile should be done in 3-4 mins, you add on a little time as you wouldn't run three miles with the same tempo as 1.5 but should no add more than 5 mins. So 10x2+3+5=28. So you are average. You will have to try a damn sight harder if you want to impress.