An inspector randomly selects three parts from a lot that contains 3 defective and 4 nondefective parts. What is the probability that the inspector finds exactly 1 defective part?

Respuesta :

Answer:

[tex]P(X=k)= \frac{(MCk)(N-M C n-k)}{NCn}[/tex]  

For this case N = 7, M = 3, n =3, k=1

[tex]P(X=1)= \frac{(3C1)(7-3 C 3-1)}{7C3} = \frac{3*6}{35}= \frac{18}{35}= 0.514[/tex]  

Step-by-step explanation:

Previous concepts

The hypergeometric distribution is a discrete probability distribution that its useful when we have more than two distinguishable groups in a sample and the probability mass function is given by:

[tex]P(X=k)= \frac{(MCk)(N-M C n-k)}{NCn}[/tex]  

Where N is the population size, M is the number of success states in the population, n is the number of draws, k is the number of observed successes  

The expected value and variance for this distribution are given by:

[tex]E(X)= n\frac{M}{N}[/tex]

[tex]Var(X)=n \frac{M}{N}\frac{N-M}{N}\frac{N-n}{N-1}[/tex]

For this case N = 7, M = 3, n =3, k=1

Solution to the problem

For this case we want this probability:

[tex] P(X=1)[/tex] and if we use the probability mass function we got:

[tex]P(X=1)= \frac{(3C1)(7-3 C 3-1)}{7C3} = \frac{3*6}{35}= \frac{18}{35}= 0.514[/tex]