Question

There are 5 pens in a container on your desk. Among them, 3 will write well but 2 have defective ink cartridges. You will select 2 pens (without replacement) to take to a business appointment. Select the most appropriate statement for each part (a-e) when considering calculating the probability that both pens are defective.

a. Let X: the number of defective pens selected. X is a random variable. [Select ]
b. For each pen chosen from the container, we can consider "Defective" as the success and "Working" as the failure since we are interested in both pens being defective. [ Select] -
c. X is well approximated by a Binomial Random Variable X-Bin(n=2. pi=2/5) True
d. If the first pen was replaced before the second pen was selected (sampling with replacement), then X would be very well approximated by a Binomial Random Variable X-Bin(n=2, pi=2/5) True
e. Had you been drawing 2 pens (without replacement) from a container of 25 pens, X would be better approximated by a Binomial Random Variable.

Answer 1

Kindly check explanation

Explanation:

Total Number of pens = 5

Number of defective pens = 2

Number of non-defective pens = 3

A.) number of defective pens selected :

X : {0, 1, 2}

It is possible that no defective pen will be selected ; 1 defective will be chosen or both pens are defective.

2.)

Defective as Success (since selecting a defective pen is the point of interest.

3.)

Since selection is done without replacement

Probability of success per selection is different for each selection ;

Number of defective = 2

Number of observations = 5

P(success on first selection) = 2/5

P(success on second selection) = 1/4

Hence, X is not well approximated by a binomial random variable.

4.) if selection is done with replacement ; then then the probability of success per selection will be the Same for each selection made. Hence, X will be well approximated by a binomial Random variable.

5.) If sampling is done without replacement, then the the hypergeometric function will be a more effective approximation.