Question

The owner of a computer company claims that the proportion of defective computer chips produced at plant A is higher than the proportion of defective chips produced by plant B. A quality control specialist takes a random sample of 80 chips from production at plant A and determines that there are 12 defective chips. The specialist then takes a random sample of 90 chips from production at plant B and determines that there are 10 defective chips. Let pA = the true proportion of defective chips from plant A and pB = the true proportion of defective chips from plant B. Which of the following is a correct statement about the conditions for this test?

A. The random condition is not met.
B. The 10% condition is not met.
C. The Large Counts Condition is not met.
D. All conditions for inference are met.

Answer 1

D. All conditions for inference are met.

Explanation:

For the 10% condition :

x / n ; x = number of defective samples ; n = sample size

For Plant A :

x / n = 12 / 80 = 0.15 (> 0.10)

Plant B:

x / n = 10 / 90 = 0.11 (> 0.10)

The sample sizes are large enough ; n > 30

The questions stated that samples were chosen at random.

Hence, all conditions for inference are met.