1. Answers to Practice Questions 7.4, 7.10, 7.16 (8.4, 8.10, 8.16)
Use the decision tree to help decide which test to use!

2. Healey #7.4/8.4 Problem information: Use the 5-step method….
 = = 502
σ = 95 (note: question gives pop’n value)
n = 152
Use the 5-step method….
Steps 1 - 3
1 random sample, Interval-ratio
Sample is large n ≥ 100, normal
z-test
Question asks “Is there a significant difference?”
2-tailed test, α=.05, z=±1.96
Ho: H1:

3. #7.4/8.4 cont.
Step 4:
Step 5:
Zobtained>Zcritical therefore reject Ho
The difference is significant and not random chance
The first year students’ score is significantly different from the national population (Zobt=6.36, α=.05)

4. Healey #7.10/8.10 Problem information: Use the 5-step method….
 = $ = $98
s = $5 (question gives sample value)
n = 36
Use the 5-step method….
Steps 1 - 3
1 random sample, Interval-ratio
Sample is small, n < 100, t-distribution
t-test
Question asks “Is the a difference significant?”
2-tailed test, df=n-1=35, α=.05, t=±2.042 (more conservative)
Ho: H1:

5. Healey #7.10/8.10 cont. Step 4: Step 5:
tobtained>tcritical therefore reject Ho
The difference is significant and not random chance
Property tax for the sample is significantly different from the national population (tobt=-37.86, df=35, α=.05)

6. Healey 7.16/8.16 Problem information: Use the 5-step method….
Pu = .18 (18%) Ps = .217 (21.7%)
N = 323
Use the 5-step method….
Steps 1 - 3:
1 random sample, Nominal
Sample is large n ≥ 100, normal
z-distribution (z-test)
Question asks “is the difference significant?”
2-tailed test, α=.05, z=±1.96
Ho: Ps=Pu H1:Ps≠Pu

7. #7.16/8.16 cont.
Step 4:
Step 5:
Zobtained<Zcritical therefore fail to reject Ho
The difference is not significant and is random chance
There is no significant difference in unemployment rates.
note that if a one-tailed test had been used instead (i.e. to test if the sample unemployment rate is higher) then Zcritical=+1.65, and Ho would be rejected!