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Unformatted text preview: Revised 01/19/2010 2201_Quiz3A.docm EXST 2201
Quiz 3A
Name: Section: Score: Directions: This quiz will be available on Moodle after the Chapter 8 lectures 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. Classify the following scenarios.
1A. Sample 1: The weights (lbs) of 19 newborn females.
Sample 2: The weights (lbs) of 19 newborn males.
•
• Paired samples.
Independent samples. 1B. Sample 1: The scores (points) of 13 students who took the ACT.
Sample 2: The scores (points) of 13 other students who took the SAT.
•
• Paired samples.
Independent samples. 1C. Sample 1: The pretraining weights (lbs) of 17 athletes.
Sample 2: The posttraining weights (lbs) of the same 17 athletes.
•
• Paired samples.
Independent samples. Page 1 of 7 Revised 01/19/2010 2201_Quiz3A.docm 2. A weight–lifting coach claims that weight–lifters can increase their strength by
taking a certain supplement. To test his theory, the coach randomly selects 9
athletes and gives them a strength test using a bench press. Thirty days later,
after regular training using the supplement, they are tested again. The results
are listed below. Test the claim that the supplement is effective in increasing
the athlete’s strength. Use significance 0.10 and assume that the data are
distributed normally.
Before:
After:
Difference: 215
225
–10 Difference: n
9 240
245
–5
D
¯ –4.78 188
188
0 212
210
2 275
282
–7 260
275
–15 225
230
–5 200
195
5 s
6.24 2A. What is the appropriate set of hypotheses (H0, H1)?
•
•
•
• µd = 0,
µd ≠ 0,
µd = 0,
µd = 0, µd ≠ 0
µd = 0
µd < 0
µd > 0 2B. What is the correct value of the test statistic?
•
•
•
• –2.30
+6.51
–4.44
–6.51 2C. What is the correct P–value for this test statistic?
•
•
•
• 0.025
0.050
0.020
0.100 2D. Does the supplement significantly increase the athletes’ strength?
•
•
•
• Yes.
No.
Sometimes.
Depends on distribution. Page 2 of 7 182
190
–8 Revised 01/19/2010 2201_Quiz3A.docm 3. A study was conducted to determine if the salaries of elementary school
teachers from two neighboring districts were equal. A sample of 15 teachers
from each district was randomly selected. Test the claim that the salaries from
both districts are equal. Use significance 0.05 and assume that the data are
distributed normally.
District 1:
District 2: n
15
15 x
¯
$28,900
$30,300 s
$2,300
$2,100 3A. What is the appropriate set of hypotheses (H0, H1)?
•
•
•
• µ1 – µ2 = 0,
µ1 – µ2 ≠ 0,
µ1 – µ2 = 0,
µ1 – µ2 = 0, µ1 – µ2 ≠ 0
µ1 – µ2 = 0
µ1 – µ2 < 0
µ1 – µ2 > 0 3B. What is the correct confidence interval?
•
•
•
• (–2475, –325)
(–2100, –700)
(–2975, 175)
(–3125, 325) 3C. Are the salaries of the teachers from the two districts different?
•
•
•
• Yes.
No.
Sometimes.
Depends on distribution. Page 3 of 7 Revised 01/19/2010 2201_Quiz3A.docm 4. (Question 4 subparts below)
4A. How many populations (columns of data) is ANOVA used for?
•
•
•
• 0
1
2
3 or more 4B. What statistical distribution does ANOVA use to make a decision?
•
•
•
• z Distribution
F Distribution
p Distribution
t Distribution 4C. In a oneway ANOVA, when can a factor have only one level?
•
•
•
• Always
Never
Sometimes
It depends 4D. What is the null hypothesis in a one–way ANOVA with three populations?
•
•
•
• µ1 = µ2 = µ3
µ1 ≠ µ2 = µ3
µ1 = µ2 ≠ µ3
µ1 ≠ µ2 ≠ µ3 4E. Which of the following is NOT an assumption of ANOVA?
•
•
•
• Random samples.
Dependent samples.
Normally distributed.
Equal standard deviations. Page 4 of 7 Revised 01/19/2010 2201_Quiz3A.docm 5. (Question 5 subparts below)
5A. The ANOVA method consists of:
1) An overall test of population means and
2) Followup analysis giving specific details.
•
•
•
• True
False
Sometimes
It depends 5B. The F–statistic is computed as a fraction with the variation _A_ in the
numerator and with the variation _B_ in the denominator.
•
•
•
• A = Around samples
A = Within samples
A = Between samples
A = Through samples B = Through samples
B = Between samples
B = Within samples
B = Around samples 5C. The total sum of squares (SSTotal) can be decomposed as:
•
•
•
• SSModel * SSError
SSModel – SSError
SSModel / SSError
SSModel + SSError 5D. The F–statistic in ANOVA is computed as:
•
•
•
• MSModel * MSError
MSModel / MSError
MSModel – MSError
None of the above. 5E. What are the correct values to fill the two blanks (_A_ and _B_) in the
ANOVA table below?
Source
Model
Error
Corrected Total
•
•
•
• DF
2
_A_
42 Sum of
Squares
246
116
1406 A = 40, B = 4.24
A = 42, B = 152
A = 44, B = 94
A = 40, B = 0.24 Page 5 of 7 Mean
Square
123
29 FValue
_B_ PValue
P Revised 01/19/2010 2201_Quiz3A.docm 6. (Question 6 subparts below)
6A. For a significance level 0.05, a P–value of 0.025 in an ANOVA means that
the data give evidence that the means of all populations are equal.
•
•
•
• True
False
Sometimes
It depends 6B. Which population means can be considered significantly different in the
Tukey Grouping shown below?
Population
3
2
4
1
5
•
•
•
• Mean Tukey Grouping
17.95
A
15.25
A
B
12.80
A
B
11.15
B
9.05
C 1, 3 and 5
2 and 4
3 and 5
1, 2, 3 and 4 7. An engineer wants to know if the strengths of two separate concrete mixes are
different. He randomly selects 9 cylinders of mixture 670301 (sample #1)
and 10 cylinders of mixture 670400 (sample #2). After 28 days, he measures
the strength (in pounds per square inch) of the 6 by 12 inch cylinders and
obtains the information below. Use significance level 0.05.
Box plot = all points inside fences.
Normal probability plot = all points inside bounds.
Sample
670301
670400 #
1
2 n
9
10 x
¯
3,669
4,483 s
458.5
473.7 7A. What is the appropriate test procedure?
•
•
•
• Twosample ztest of the mean.
Twosample ttest of the mean.
Twosample ztest of proportion.
Pairedsample ttest of the mean. Page 6 of 7 Revised 01/19/2010 2201_Quiz3A.docm 7B. What is the appropriate set of hypotheses (H0, H1)?
•
•
•
• µ1 – µ2 = 0,
µ1 – µ2 ≠ 0,
µ1 – µ2 = 0,
µ1 – µ2 = 0, µ1 – µ2 ≠ 0
µ1 – µ2 = 0
µ1 – µ2 < 0
µ1 – µ2 > 0 7C. What is the correct magnitude of the critical value?
•
•
•
• 2.110
2.093
1.734
2.306 7D. What is the correct value of the test statistic?
•
•
•
• +1.96
+3.80
–3.80
+0.018 7E. What is the correct confidence interval?
•
•
•
• (–904, –473)
(–1307, –321)
(–1061, –567)
(–1061, 567) 7F. Are these concrete mixes significantly different in strength?
•
•
•
• Yes.
No.
Sometimes.
Maybe. Page 7 of 7 ...
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This note was uploaded on 05/13/2010 for the course EXST 2201 taught by Professor Mckenna during the Spring '08 term at LSU.
 Spring '08
 McKenna

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