Routing Routing
Algorithm Algorithm
A B
Avg. Avg.
Packet Packet
Delay (in Delay (in
msec) msec) A-B
115.0 125.3 -10.3
89.3 97.6 -8.3
102.1 85.3 16.8
94.3 101.3 -7.0
117.3 112.7 4.6
120.3 87.9 32.4
98.9 104.2 -5.3
87.6 96.3 -8.7
104.5 113.2 -8.7
Avg. Diff ………………. 0.6
STD Dev Diff ……… 14.8
alpha 0.05
T[1-alpha/2,9-1] 2.306
Two packet routing algorithms are being evaluated.
Experiments were conducted by injecting the same
workload in the network and measuring the average
end-to-end packet delay. The results of the various
experiments are shown in the table above.
Can you say with 95% confidence that routing algorithm A
is better than algorithm B?
95% Confidence interval for the difference:
Lower Bound -10.7682
Upper Bound 11.99041
The confidence interval for the difference includes zero. We cannot say that A and B are different at the 95% confidence level.
at the 95% confidence level.
CPU Time (Sec) Question: Is System A faster than system B at 90% confidence?
System A System B
1.3779 0.9584 na 24
0.0457 0.5726 nb 29
1.4415 1.3915 xa-bar 2.1719
1.3589 0.8075 xb-bar 1.9642
0.6898 0.1344 sa 2.01424
0.7076 0.1277 sb 2.72331
3.9083 1.8032 xa-bar - xb - bar 0.2077
2.2081 1.2048 stdev-diff 0.651757
0.9244 9.5949 deg-freed 48.42747
6.5770 4.9107
4.4775 0.2834 alpha 0.1
4.6199 0.3841 T[1-alpha/2,df] 1.677224
0.1775 0.0812 90% conf. interval
0.3354 2.1362 Lower Bound -0.88541
0.3687 4.6396 Upper Bound 1.300875
0.0956 1.0127
1.2116 2.9434 The interval includes zero.
3.8814 1.0844 There is no signficant statistical differerece at the 90% confidence level.
0.2922 0.7860
3.0970 2.1536
3.2150 1.4948
1.2880 11.7346
3.0046 0.9436
6.8230 3.1111
0.7478
0.3845
0.2354
0.9951
0.3045