In: Statistics and Probability
Back for more O-rings! After a catastrophic failure of your
injection mold die, the production team has rebuilt the equipment
and production is running smoothly again. However, management wants
to be sure the quality after the repairs is the same as before.
Taking it on faith that σ = 0.030 grams before the failure, you
conduct a quick experiment on a batch produced after the failure,
and you measure s = 0.036 grams from a random sample of 25
O-rings.
a) Based on this experiment, can you conclude the injection mold
process is exhibiting the same variance before and after the
repair? Show all of your work
b) The management brings in another production batch, produced
before the failure, and wants you to compare the variances of this
batch with the batch from part (a). You collect 30 random O-rings
from this batch and measure the sample standard deviation, s.
Assuming a 2-sided alternative, what is the lowest value of s you
could measure and still be able to conclude the two batches have
identical variances? Show all of your work.