May 26'23

Exercise

Dental claims experience was collected on 6480 policies. There were a total of 9720 claims on these policies. The following table shows the number of dental policies having varying numbers of claims.

Number of Claims Number of Policies
0 1282
1 2218
2 1856
3 801
4 235
5 81
6 or more 7
Total 6480


Calculate the chi-squared statistic to test if a Poisson model with no predictors provides an adequate fit to the data.

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Copyright 2023. The Society of Actuaries, Schaumburg, Illinois. Reproduced with permission.

May 26'23

Key: C

The average number of claims on a policy is 9720/6480 = 1.5. Using this as the parameter of a Poisson distribution yields the following table of actual (given) and expected (calculated) policies with given numbers of claims:

Number of Claims ActualNumber of Policies Poisson Probability ExpectedNumber of Policies Chi-square
0 1282 0.2231 1445.69 18.53
1 2218 0.3347 2168.86 1.11
2 1856 0.2510 1626.48 32.39
3 801 0.1255 813.24 0.18
4 235 0.0471 305.21 16.15
5 81 0.0141 91.37 1.18
6 or more 7 0.0045 29.16 16.84
Total 6480 1.0000 6480.01 86.38

Copyright 2023. The Society of Actuaries, Schaumburg, Illinois. Reproduced with permission.

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