Homework ch. 20-21

1
Homework ch. 20-21
2
1. A toy manufacturer claims that at least 23
of the fourteen year old residents of a certain
city own skateboards. A sample of 400 fourteen
year olds shows that 70 own a skateboard. Test
this claim at an a0.05.

• H0 p 0.23 claim H1 p lt 0.23
• Reject the null
• There is enough information to reject the that at
  least 23 of the fourteen year old residents of a
  certain city own skateboards.

3
2. A past study found that at most 32 of people
who have been in a plane crash have died. In a
sample of 100 people who were in a plane crash 38
died. Use an a0.05 to test the claim from the
past study.

• H0 p 0.32 claim H1 p gt 0.32
• Not reject the null
• There is not enough information to reject the
  claim that at most 32 of people who have been in
  a crash have died.

4
A telephone company wants to advertise that more
than 30 of all of its customers have at least
two telephones. To support this advertisement,
the company selects a sample of 200 customers and
finds that 72 have more than two telephones.
Use an a0.01 to test this add.

• H0 p 0.30 H1 p gt 0.30 claim
• Not reject the null
• There is not enough information to support the
  claim that more than 30 of all of its customers
  have at least two telephones

5
Researchers suspect that 18 of all high school
students smoke at least one pack of cigarettes a
day. At Wilson high school, with an enrollment
of 300 students, a study found 50 students smoke
at least one pack of cigarettes a day. At and
a0.10 test what the researchers suspect.

• H0 p 0.18 claim H1 p ? 0.18
• Not reject the null
• There is not enough information to reject the
  claim that 18 of all high school students smoke
  at least one pack of cigarettes a day