Web Page Diagnostics in Performance Testing

Hi All, In a load test we got the analysis report as follows: Transaction Avg Response time Server time NW time Receive time 1. Txn 1 36.027 s 20.529s 0.761s 42.689s 2. Txn 2 26.419 6.444 0.22 39.881 3. Txn 3 26.865 7.407 0.249 39.423 4. Txn 4 26.451 6.527 0.224 39.596 5. Txn 5 32.188 10.233 0.352 51.219 6. Txn 6 25.976 6.232 0.201 37.667 We used 500 users for this test and ran for 4 hrs. We used 1% of Vuser Sampling for Web page Diagnostics. Here,the Avg Response times of all the transactions are very much smaller when compared to Web page data from the samples ( First Buffer Time plus the Receive Time). Can any one explain me , 1 . What causes this much difference in the times? 2 . What effect does it have in the times in having the different percentages of the Vuser samples? 3. How is the sampling of Vusers done and at what times does the values are taken for Page diagnosis? Thanks in advance, Francis.