In: Statistics and Probability
14% of individuals insured by all-driver automobile insurance company have at least one traffic ticket. For a sample of 125 insured individuals, what is the probability that between 11 and 25 of them have received at least one ticket
Normal approximation for binomial distribution: P(X < A) = P(Z < (A - mean)/standard deviation)
Sample size, n = 125
P(at least one traffic ticket), p = 0.14
q = 1 - p = 0.86
Mean = np
= 125 x 0.14
= 17.5
Standard deviation =
= 3.88
P(between 11 and 25 of them have received at least one ticket) = P(10.5 < X < 25.5) (with continuity correction)
= P(X < 25.5) - P(X < 10.5)
= P(Z < (25.5 - 17.5)/3.88) - P(Z < (10.5 - 17.5)/3.88)
= P(Z < 2.06) - P(Z < -1.80)
= 0.9803 - 0.0359
= 0.9444