Question

Eighteen individuals are scheduled to take a driving test at a particular DMV office on a certain day, eight of whom will be taking the test for the first time. Suppose that six of these individuals are randomly assigned to a particular examiner, and let X be the number among the six who are taking the test for the first time. a. What kind of a distribution does X have (name and values of all parameters)

Answer 1

X has an hypergeometric distribution, with parameters:

Size of the population is N = 18.

Size of the sample is n = 6.

Number of successes n is k = 8.

Explanation:

The people are chosen without replacement, which means that the hypergeometric distribution is used.

Hypergeometric distribution:

The probability of x sucesses is given by the following formula:

`P(X = x) = h(x,N,n,k) = (C_(k,x)*C_(N-k,n-x))/(C_(N,n))`

In which:

x is the number of sucesses.

N is the size of the population.

n is the size of the sample.

k is the total number of desired outcomes.

Combinations formula:

`C_(n,x)` is the number of different combinations of x objects from a set of n elements, given by the following formula.

`C_(n,x) = (n!)/(x!(n-x)!)`

Eighteen individuals are scheduled to take a driving test at a particular DMV office on a certain day, eight of whom will be taking the test for the first time.

This means that
`N = 18, k = 8`

We consider a success being a person taking the test for the first time, because X is the number among the six who are taking the test for the first time.

Suppose that six of these individuals are randomly assigned to a particular examiner.

This means that
`n = 6`

a. What kind of a distribution does X have (name and values of all parameters)

X has an hypergeometric distribution, with parameters:

Size of the population is N = 18.

Size of the sample is n = 6.

Number of successes n is k = 8.