There is a 3%probability that a selected life insurance application contains an error. An auditor randomly selects100 applications. Using the Poisson approximation to the Binomial, calculate the probability that 951/% or less of the applications are error-free.
Q. There is a 3% probability that a selected life insurance application contains an error. An auditor randomly selects100 applications. Using the Poisson approximation to the Binomial, calculate the probability that 951/% or less of the applications are error-free.
Understand the problem and parameters: Understand the problem and determine the parameters for the Poisson approximation.We are given that the probability of an error in a single application is 3%, or 0.03. We are also given that 100 applications are selected. We want to find the probability that 95% or less of these applications are error-free, which means 5% or more contain an error. To use the Poisson approximation, we need to calculate the mean (λ) of the distribution, which is the expected number of errors in the 100 applications.λ=n×pwhere n is the number of trials (applications) and p is the probability of success (error in an application).
Calculate the mean: Calculate the mean λ of the Poisson distribution.λ=100×0.03λ=3The mean number of errors λ is 3.
Use Poisson distribution: Use the Poisson distribution to find the probability that there are k errors, where k ranges from 0 to the number corresponding to 5% of the applications (since we want 95% or less to be error-free).First, we need to find the number of applications that correspond to 5% of 100, which is 5 applications. We will sum the probabilities of having 0, 1, k0, k1, k2, and 5 errors.The Poisson probability mass function is given by:k4where k is the actual number of successes (errors), k6 is the mean number of successes, and k7 is the base of the natural logarithm (approximately k8).
Calculate probabilities for k: Calculate the probabilities for k=0 to k=5 using the Poisson probability mass function.P(0;3)=0!e−3⋅30=1e−3P(1;3)=1!e−3⋅31=13⋅e−3P(2;3)=2!e−3⋅32=29⋅e−3P(3;3)=3!e−3⋅33=627⋅e−3P(4;3)=4!e−3⋅34=2481⋅e−3P(5;3)=5!e−3⋅35=120243⋅e−3
Sum probabilities for 95%: Sum the probabilities from k=0 to k=5 to find the total probability that 95% or less of the applications are error-free.P(95% or less error-free)=P(0;3)+P(1;3)+P(2;3)+P(3;3)+P(4;3)+P(5;3)P(95% or less error-free)=e−3+3⋅e−3+29⋅e−3+627⋅e−3+2481⋅e−3+120243⋅e−3
Perform calculations for total probability: Perform the calculations to find the total probability.P(95% or less error-free)=e−3×(1+3+4.5+4.5+3.375+2.025)P(95% or less error-free)=e−3×(18.4)Now we need to calculate e−3×18.4 using a calculator or software that can handle the exponential function.
Calculate final probability: Calculate e−3×18.4 to get the final probability.P(95% or less error-free)≈0.0498×18.4P(95% or less error-free)≈0.91632
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