Unformatted text preview: Revised 01/19/2010 2201_Quiz4.docm EXST 2201
Quiz 4
Name: Section: Score: Directions: This quiz will be available on Moodle after the lectures for chapter 10 have been
given. Mark your answers on this printout. When the quiz is available on
Moodle, record your answers in the Moodle quiz and submit them for grading.
You may take the quiz only once and you will have an hour and a half to
complete it, so be sure of your answers before you start the Moodle quiz.
1. Previous research shows that 65% of murders are committed with a firearm.
If 150 murders are randomly selected, use the normal approximation to the
binomial to determine what is the probability that:
1A. 100 or more murders are committed with a firearm?
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•
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• 0.452
0.548
0.367
0.164 1B. 90 or fewer murders are committed with a firearm?
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• 0.115
0.367
0.164
0.452 1C. 100 ≤ murders ≤ 105 are committed with a firearm?
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•
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• 0.452
0.548
0.115
0.282 Page 1 of 5 Revised 01/19/2010 2201_Quiz4.docm 2. In a poll of 2,208 randomly selected Americans, 1,247 thought that state laws
regarding child safety restraints in vehicles should be strengthened.
2A. What is the point estimate of the population proportion?
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• 1.77
0.19
0.50
0.56 2B. What is the value of the condition to use the normal approximation?
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• 1,247
544
–3,012
306 2C. Is it appropriate to compute a CI estimate of proportion when the
condition to use the normal approximation is 6.8345?
•
•
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• Yes.
No.
Sometimes.
Depends on distribution. 2D. What is the 92% CI estimate of proportion?
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•
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• (0.54, 0.60)
(0.54, 0.56)
(0.54, 0.58)
(0.55, 0.57) Page 2 of 5 Revised 01/19/2010 2201_Quiz4.docm 3. A study finds that 85% of teachers use the Internet to teach. A researcher claims
that the percentage has recently increased. She collects a random sample of
340 teachers and finds that 302 of the teachers used the Internet to teach.
3A. What is the population proportion (p) and the sample proportion ( ) for
this set of data?
•
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• 0.89, 0.85
0.85, 0.89
0.85, 0.85
0.89, 1.12 3B. What is the magnitude of the critical value for a onetailed test of
proportion with significance 0.10?
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• 2.33
1.75
1.64
1.28 3C. What is the value of the test statistic to test if the population proportion is
0.85 at significance 0.10?
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• –1.75
1.55
2.06
2.47 3D. What decision would be made for a onetailed test that the population
proportion is 0.85 at significance 0.10?
•
•
•
• Do not reject the null.
Reject the null.
Sometimes reject the null.
Do not reject the alternative. Page 3 of 5 Revised 01/19/2010 2201_Quiz4.docm 4. On average it has been found in grocery stores that 1% of scanned items are
priced incorrectly. Recently, a sample of 1,034 randomly selected items were
scanned and 20 were found to be priced incorrectly. Has the rate of incorrectly
priced items changed?
4A. What is the appropriate test procedure?
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•
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• zTest of the mean.
tTest of the mean.
zTest of the proportion.
None of these. 4B. What is the appropriate null hypothesis?
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•
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• µ = 0.01
µ ≤ 0.01
µ ≠ 0.01
µ ≥ 0.01 4C. What is the appropriate alternative hypothesis?
•
•
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• µ = 0.01
µ < 0.01
µ ≠ 0.01
µ > 0.01 4D. Assume it should be a ttest and the sample size is 105. What decision
would be made for a hypothesis test at significance 0.05 if you calculated
a test statistic of 0.94?
•
•
•
• Do not reject the null.
Reject the null.
Sometimes reject the null.
Do not reject the alternative. Page 4 of 5 Revised 01/19/2010 2201_Quiz4.docm 5. In the initial test of the Salk vaccine for polio, 400 children were selected and
divided into two groups of 200. One group was vaccinated with the Salk vaccine
while the second group was vaccinated with a placebo. Of those vaccinated with
the Salk vaccine, 33 later developed polio. Of those vaccinated with the placebo,
115 later developed polio. Test the claim that the Salk vaccine is effective in
lowering the rate of polio. Use significance 0.01 and assume that the data are
distributed normally.
5A. What is the appropriate set of hypotheses (H0, H1)?
•
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• psalk – pplacebo = 0,
psalk – pplacebo ≠ 0,
psalk – pplacebo = 0,
psalk – pplacebo = 0, psalk – pplacebo ≠ 0
psalk – pplacebo = 0
psalk – pplacebo < 0
psalk – pplacebo > 0 5B. What are the correct proportions (psalk, pplacebo)?
•
•
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• 0.095, 0.435
0.575, 0.165
0.165, 0.575
0.435, 0.095 5C. What is the correct value of the test statistic?
•
•
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• –0.23
–1.38
–9.54
–8.49 5D. What is the correct confidence interval?
•
•
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• (–0.52, –0.30)
(–0.30, 0.52)
(–0.53, 0.30)
(0.30, 0.53) 5E. Was the Salk vaccine effective at reducing the rate of polio?
•
•
•
• Yes.
No.
Sometimes.
Depends on distribution. Page 5 of 5 ...
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Full Document
 Spring '08
 McKenna
 Normal Distribution, Null hypothesis, Statistical hypothesis testing, µ, psalk – pplacebo

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