Question

Two different types of injection-molding machines are used to form plastic parts. A part is considered defective if it has excessive shrinkage or is discolored. Two random samples, each of size 300, are selected and 15 defective parts are found in the sample from machine 1 and 8 defective parts are found in the sample from machine 2.

What type of hypothesis test should you use to determine if both machines produce the same fraction of defective parts?

Group of answer choices

a) 2 Sample Prop T-Test

b) Paired T-Test

c) 2 Sample Z-Test

d) 2 Sample Prop Z-Test

Answer 1

Solution:

n₁ = 300 , n₂ = 300

x₁ = 15 , x₂ = 8

We are comparing two proportions.

So we use 2 sample Proportion test.

Z distribution is used to test the two proportions.

So , answer is

2 Sample Prop Z-Test

Option d) is correct.