Question

A car manufacturer has two production plants in different cities. Every day, plant A produces 120 of a certain

type of car, while plant B produces 80 of those cars. On average, all of these cars have a paint thickness of
0.04 mm with a standard deviation of 0.003 mm.
Every day, quality control experts take separate random samples of 10 cars from each plant and calculate the
mean paint thickness for each sample. They then look at the difference between those sample means.
Consider the formula:
031-32 =
02
+
ni 12
Why is it not appropriate to use this formula for the standard deviation of TA
IB?

Answer 1

Answer: We cannot assume independence of the cars sampled from plant B.

Explanation:

Answer 2

Answer: We cannot assume independence for the cars sampled from plant B.

Step-by-step explanation: Khan Academy “With a sample size of 10 cars, we need at least 100 cars in the population to assume independence based on the 10% condition, but there are only 80 cars made each day at plant B.”