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Dynamic Bayesian Approach for Detecting Cheats in Multi-Player ...

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16 S.F. Yeung, John C.S. Lui<br />

probability (%)<br />

100<br />

90<br />

80<br />

70<br />

60<br />

50<br />

40<br />

30<br />

20<br />

10<br />

0<br />

0 50 100 150 200 250 300 350 400 450 500<br />

(a) cheater cb1<br />

probability (%)<br />

100<br />

90<br />

80<br />

70<br />

60<br />

50<br />

40<br />

30<br />

20<br />

10<br />

Inferred probability of cheat<strong>in</strong>g<br />

timeframe<br />

Inferred probability of cheat<strong>in</strong>g<br />

0<br />

0 50 100 150 200 250 300 350 400 450 500<br />

timeframe<br />

(d) honest player hb1<br />

Accuracy (%)<br />

100<br />

90<br />

80<br />

70<br />

60<br />

50<br />

40<br />

30<br />

20<br />

10<br />

0<br />

0 50 100 150 200 250 300 350 400 450 500<br />

(g) cheater cb1<br />

Accuracy (%)<br />

100<br />

90<br />

80<br />

70<br />

60<br />

50<br />

40<br />

30<br />

20<br />

10<br />

Aim<strong>in</strong>g accuracy<br />

timeframe<br />

Aim<strong>in</strong>g accuracy<br />

0<br />

0 50 100 150 200 250 300 350 400 450 500<br />

timeframe<br />

(j) honest player hb1<br />

probability (%)<br />

100<br />

90<br />

80<br />

70<br />

60<br />

50<br />

40<br />

30<br />

20<br />

10<br />

Inferred probability of cheat<strong>in</strong>g<br />

0<br />

0 50 100 150 200 250 300 350 400 450 500<br />

(b) cheater cb2<br />

probability (%)<br />

100<br />

90<br />

80<br />

70<br />

60<br />

50<br />

40<br />

30<br />

20<br />

10<br />

timeframe<br />

Inferred probability of cheat<strong>in</strong>g<br />

0<br />

0 50 100 150 200 250 300 350 400 450 500<br />

timeframe<br />

(e) honest player hb2<br />

Accuracy (%)<br />

100<br />

90<br />

80<br />

70<br />

60<br />

50<br />

40<br />

30<br />

20<br />

10<br />

0<br />

0 50 100 150 200 250 300 350 400 450 500<br />

(h) cheater cb2<br />

Accuracy (%)<br />

100<br />

90<br />

80<br />

70<br />

60<br />

50<br />

40<br />

30<br />

20<br />

10<br />

Aim<strong>in</strong>g accuracy<br />

timeframe<br />

Aim<strong>in</strong>g accuracy<br />

0<br />

0 50 100 150 200 250 300 350 400 450 500<br />

timeframe<br />

(k) honest player hb2<br />

probability (%)<br />

100<br />

90<br />

80<br />

70<br />

60<br />

50<br />

40<br />

30<br />

20<br />

10<br />

Inferred probability of cheat<strong>in</strong>g<br />

0<br />

0 50 100 150 200 250 300 350 400 450 500<br />

(c) cheater cb2<br />

probability (%)<br />

100<br />

90<br />

80<br />

70<br />

60<br />

50<br />

40<br />

30<br />

20<br />

10<br />

timeframe<br />

Inferred probability of cheat<strong>in</strong>g<br />

0<br />

0 50 100 150 200 250 300 350 400 450 500<br />

timeframe<br />

(f) honest player hb3<br />

Accuracy (%)<br />

100<br />

90<br />

80<br />

70<br />

60<br />

50<br />

40<br />

30<br />

20<br />

10<br />

Aim<strong>in</strong>g accuracy<br />

0<br />

0 50 100 150 200 250 300 350 400 450 500<br />

(i) cheater cb2<br />

Accuracy (%)<br />

100<br />

90<br />

80<br />

70<br />

60<br />

50<br />

40<br />

30<br />

20<br />

10<br />

timeframe<br />

Aim<strong>in</strong>g accuracy<br />

0<br />

0 50 100 150 200 250 300 350 400 450 500<br />

timeframe<br />

(l) honest player hb3<br />

Fig. 6 Result of Experiment 1. Cheaters have probabilities fluctuat<strong>in</strong>g around the threshold, as illustrated <strong>in</strong> the sub-figures (a)-(c), while honest<br />

players have probabilities well below the threshold, as illustrated <strong>in</strong> sub-figures (d)-(f). For comparison, the aim<strong>in</strong>g accuracies of the players are<br />

shown <strong>in</strong> the sub-figures (g)-(l) respectively.

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