Transcript 9.2 Power Point

Chapter 9: Hypothesis
Testing
Section 2: Tests Involving the
Mean (Large Samples)
Example
• A sports biologist claimed that female
distance runners tend to be taller on the
average than women in general, who have
an average height of 64 inches. To study
this, she obtained a random sample of 40
female distance runners and recorded
their heights with the following results: x =
65.6 inches and s = 3.3 inches. Using
these results, test the claim at the 5% level
of significance.
Example
• A bus company advertised a mean time of
150 minutes for a trip between two cities.
A consumer group had reason to believe
that the mean times was more than 150
minutes. A sample of 40 trips showed a
mean of 153 minutes and a standard
deviation of 7.5 minutes. Test the claim at
the 5% level of significance.
Example
• The owner of an artesian well-drilling
company suspected that, for a large tract
of development land, the average depth of
water below the surface was less than 500
feet. A sample of 32 wells gave a mean
depth of 486 feet and a standard deviation
of 53 feet. At the 1% level of significance,
is the owner’s suspicion justified?