Usual 10.3 15.2 13.0 9.9 12.1 13.4 12.2 14.9 13.2 12.0
Device 13.6 15.7 12.9 13.2 12.9 13.4 12.1 13.9 15.7 15.4 17.4
37.
S
amples from two makers
of ball bearings are collected, and their diameters (in
inches) are measured, with the following results:
Acme:
n1=80
,
s1=0.0395
Bigelow:
n2=120
,
s2=0.0428
Assuming that the diameters of the bearings from both companies are normally
distributed
, test the claim that there is no difference in the variation
of the
diameters
between the two companies
at the α=0.05 level.
38.
Many stores sell extended warranties for products they sell. These are very lucrative for
store owners. To learn more about who buys these warranties, a random sample was
drawn of a store’s customers who recently purchased a product for which an extended
warranty was available. Among other vari- ables, each respondent reported whether he
or she paid the regular price or a sale price and whether he or she purchased an extended
warranty.
Regular Price
Sale Price
Sample size
229 178
Number who bought extended warranty 47
25
Can we conclude at the 10% significance level that those who paid the regular price are
more likely to buy an extended warranty?
