An auto insurance company concludes that 30% of policyholders with only collision coverage will have a claim next year, 40% of policyholders with only comprehensive coverage will have a claim next year, and 50% of policyholders with both collision and comprehensive coverage will have a claim next year. Records show 60% of policyholders have collision coverage, 70% have comprehensive coverage, and all policyholders have at least one of these coverages. Calculate the percentage of policyholders expected to have an accident next year.

P( collision coverage and comprehensive coverage ) = P( collision coverage ) + P( comprehensive coverage ) - P( collision coverage or comprehensive coverage )

P( collision coverage and comprehensive coverage ) = 0.6 + 0.7 - 1

P( collision coverage and comprehensive coverage ) = 0.3

Now,

P( comprehensive coverage only ) = P( comprehensive coverage ) - P( collision coverage and comprehensive coverage )

P( comprehensive coverage only ) = 0.7 - 0.3

P( comprehensive coverage only ) = 0.4

And

P( collision coverage only) = P( collision coverage ) - P( collision coverage and comprehensive coverage )

P( collision coverage only) = 0.6 - 0.3 = 0.3

Next we make use of the Law of total probability;

P( accident ) = [P( accident ║ collision coverage only) × P( collision coverage only)] + [P( accident ║ comprehensive coverage only) × P( comprehensive coverage only)] + [P( accident ║ collision coverage and comprehensive coverage only) × P( collision coverage and comprehensive coverage only)]

so we substitute in our values;

P( accident ) = [ 30% × 0.3 ] + [ 40% × 0.4 ] + [ 50% × 0.3 ]

P( accident ) = [ 0.3 × 0.3 ] + [ 0.4 × 0.4 ] + [ 0.5 × 0.3 ]

P( accident ) = 0.09 + 0.16 + 0.15

P( accident ) = 0.4 or 40%

Therefore, 40% of policyholders are expected to have an accident next year