Complete the following exercises located at the end of each chapter and
put them into a Word document to be submitted as directed by the instructor.
Show all relevant work; use the equation editor in Microsoft Word when
necessary.
1.
Chapter 13, numbers 13.6, 13.8, 13.9,
and 13.10
2.
Chapter 14, numbers 14.11, 14.12, and
14.14
3.
Chapter 15, numbers 15.7, 15.8, 15.10
and 15.14
PSY520 – Module 5
Submit your
answers in the boxes provided. No credit will be given for responses not found
in the correct answer area.
Chapter 13:
13.6It’s
well established, we’ll assume, that lab rats require an average of 32 trials
in a complex water maze before reaching a learning criterion of three
consecutive errorless trials. To determine whether a mildly adverse stimulus
has any effect on performance, a sample of seven lab rats were given a mild
electrical shock just before each trial.
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Question:
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Steps:
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Calculations
or Logic:
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Answer:
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Given
that X5 34.89 and s5 3.02, test
the null hypothesis with t, using the .05 level of
significance.
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What is the
research hypothesis?
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What is the
null hypothesis?
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Is this a
one-tailed or two-tailed test?
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What are
the degrees of freedom?
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What is the
t critical for .05 significance?
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What is the
calculated t?
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Do you
accept or reject the null hypothesis?
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Construct a
95 percent confidence interval for the true number of trials required to
learn the water maze.
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Interpret
this confidence interval.
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13.8Assume
that on average, healthy young adults dream 90 minutes each night, as inferred
from a number of measures, including rapid eye movement (REM) sleep. An
investigator wishes to determine whether drinking coffee just before going to
sleep affects the amount of dream time. After drinking a standard amount of
coffee, dream time is monitored for each of 28 healthy young adults in a random
sample. Results show a sample mean, X,of 88 minutes and a
sample standard deviation, s, of 9 minutes.
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Question:
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Steps:
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Calculations
or Logic:
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Answer:
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Use tto
test the null hypothesis at the .05 level of significance.
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What is the
research hypothesis?
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What is the
null hypothesis?
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Is this a
one-tailed or two-tailed test?
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What are
the degrees of freedom?
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What is the
t critical for .05 significance?
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What is the
calculated t?
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Do you
accept or reject the null hypothesis?
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If
appropriate (because the null hypothesis has been rejected), construct a 95
percent confidence interval and interpret this interval.
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13.9In
the gas mileage test described in this chapter, would you prefer a smaller or a
larger sample size if you were the car manufacturer? Why? a vigorous prosecutor
for the federal regulatory agency? Why
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Question:
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Smaller or
Larger?
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Why?
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In the gas
mileage test described in this chapter, would you prefer a smaller or a
larger sample size if you were the car manufacturer?
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In the gas
mileage test described in this chapter, would you prefer a smaller or a
larger sample size if you were a vigorous prosecutor for the federal
regulatory agency?
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13.10Even
though the population standard deviation is unknown, an investigator uses zrather
than the more appropriate tto test a hypothesis at the .05
level of significance.
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Question:
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Larger or
smaller?
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Is the true
level of significance larger or smaller than .05
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Is the true
critical value larger or smaller than that for the critical z?
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Chapter 14:
14.11To
test compliance with authority, a classical experiment in social psychology
requires subjects to administer increasingly painful electric shocks to
seemingly helpless victims who agonize in an adjacent room. Each subject earns
a score between 0 and 30, depending on the point at which the subject refuses
to comply with authority—an investigator, dressed in a white lab coat, who
orders the administration of increasingly intense shocks. A score of 0
signifies the subject’s unwillingness to comply at the very outset, and a score
of 30 signifies the subject’s willingness to comply completely with the
experimenter’s orders.
Ignore the very real ethical issues raised by this type of experiment
and assume that you want to study the effect of a “committee atmosphere” on
compliance with authority. In one condition, shocks are administered only after
an affirmative decision by the committee, consisting of one real subject and
two associates of the investigator, who act as subjects but in fact merely go
along with the decision of the real subject. In the other condition, shocks are
administered only after an affirmative decision by a solitary real subject.
A total of 12 subjects are randomly assigned, in equal numbers, to the
committee condition (X1) and to the solitary condition (X2).
A compliance score is obtained for each subject. Use tto test
the null hypothesis at the .05 level of significance.
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COMMITTEE
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SOLITARY
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2
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3
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5
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8
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20
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7
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15
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10
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4
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14
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10
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0
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Question:
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Steps:
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Calculations
or Logic:
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Answer:
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|
Use tto
test the null hypothesis at the .05 level of significance.
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What is the
research hypothesis?
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What is the
null hypothesis?
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Is this a
one-tailed or two-tailed test?
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What are
the degrees of freedom?
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What is the
t critical for .05 significance?
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What is the
calculated t?
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Do you
accept or reject the null hypothesis?
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14.12To
determine whether training in a series of workshops on creative thinking
increases IQ scores, a total of 70 students are randomly divided into treatment
and control groups of 35 each. After two months of training, the sample mean IQ
(–X1) for the treatment group equals 110, and the sample mean IQ (–X2)
for the control group equals 108. The estimated standard error equals 1.80.
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Question:
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Steps:
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Calculations
or Logic:
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Answer:
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Using t,
test the null hypothesis at the .01 level of significance.
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What is the
research hypothesis?
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What is the
null hypothesis?
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Is this a
one-tailed or two-tailed test?
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What are
the degrees of freedom?
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What is the
t critical for .01 significance?
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What is the
calculated t?
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Do you
accept or reject the null hypothesis?
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If
appropriate (because the null hypothesis has been rejected), estimate the
standardized effect size, construct a 99 percent confidence interval for the
true population mean difference, and interpret these estimates.
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14.14.An
investigator wishes to determine whether alcohol consumption causes
deterioration in the performance of automobile drivers. Before the driving
test, subjects drink a glass of orange juice, which, in the case of the
treatment group, is laced with two ounces of vodka. Performance is measured by
the number of errors made on a driving simulator. A total of 120 volunteer
subjects are randomly assigned, in equal numbers, to the two groups. For
subjects in the treatment group, the mean number of errors (–X1) equals
26.4, and for subjects in the control group, the mean number of errors (–X2)
equals 18.6. The estimated standard error equals 2.4.
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Question:
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Steps:
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Calculations
or Logic:
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Answer:
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Use tto
test the null hypothesis at the .05 level of significance.
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What is the
research hypothesis?
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What is the
null hypothesis?
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Is this a
one-tailed or two-tailed test?
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What are
the degrees of freedom?
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What is the
t critical for .05 significance?
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What is the
calculated t?
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Do you
accept or reject the null hypothesis?
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Specify
the p-value for this test result.
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If
appropriate, construct a 95 percent confidence interval for the true
population mean difference and interpret this interval.
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If the test
result is statistically significant, use Cohen’s dto
estimate the effect size, given that the standard deviation, s
p, equals 13.15.
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State how
these test results might be reported in the literature, given s1 5 13.99
and s2 5 12.15.
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Chapter 15:
15.7An
educational psychologist wants to check the claim that regular physical
exercise improves academic achievement. To control for academic aptitude, pairs
of college students with similar GPAs are randomly assigned to either a
treatment group that attends daily exercise classes or a control group. At the
end of the experiment, the following GPAs are reported for the seven pairs of
participants:
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GPAs
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PAIR
NUMBER
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PHYSICAL
EXERCISE(X1)
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NO PHYSICAL
EXERCISE X2
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1
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4.00
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3.75
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2
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2.67
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2.74
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3
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3.65
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3.42
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4
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2.11
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1.67
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5
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3.21
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3.00
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6
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3.60
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3.25
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7
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2.80
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2.65
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Question:
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Calculations or Logic:
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Answer:
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Using t,
test the null hypothesis at the .01 level of significance.
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Step 1
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What is the research
problem?
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Step 2
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What is the null
hypothesis?
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What is the alternative
hypothesis?
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Step 3
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What is the decision
rule?
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Step 4
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What is the critical t?
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What is the value of t?
(you will need to calculate this)
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Step 5
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What is the decision?
(retain or reject the null hypothesis at the specified level of significance;
note the relationship between the observed and critical t scores)
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Step 6
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What is your
interpretation of the decision in relation to the original research problem?
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Specify
the p-value for this test result.
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If
appropriate (because the test result is statistically significant), use
Cohen’s dto estimate the effect size
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How might
this test result be reported in the literature?
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15.8A
school psychologist wishes to determine whether a new antismoking film actually
reduces the daily consumption of cigarettes by teenage smokers. The mean daily
cigarette consumption is calculated for each of eight teenage smokers during
the month beforeand the month afterthe fi
lm presentation, with the following results: (Note:When deciding
on the form of the alternative hypothesis, H1 , remember that
a positive difference score ( D5 X1 2 X2
) reflects a declinein cigarette consumption.)
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MEAN DAILY CIGARETTE CONSUMPTION
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SMOKER NUMBER
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BEFORE FILM (X?)
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AFTER FILM (X)?
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1
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28
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26
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2
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29
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27
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3
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31
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32
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4
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44
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44
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5
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35
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35
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6
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20
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16
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7
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50
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47
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8
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25
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23
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Question:
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Calculations or Logic:
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Answer:
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Using t,
test the null hypothesis at the .05 level of significance.
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Step 1
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What is the research
problem?
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Step 2
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What is the null
hypothesis?
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What is the alternative
hypothesis?
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Step 3
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What is the decision
rule?
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Step 4
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What is the critical t?
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What is the value of t?
(you will need to calculate this)
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Step 5
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What is the decision?
(retain or reject the null hypothesis at the specified level of significance;
note the relationship between the observed and critical t scores)
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Step 6
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What is your
interpretation of the decision in relation to the original research problem?
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Specify
the p-value for this test result.
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If
appropriate (because the null hypothesis was rejected), construct a 95
percent confidence interval for the true population mean for all difference
scores.
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If
appropriate, use Cohen’s dto obtain a standardized estimate
of the effect size.
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Interpret
the effect size.
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What might
be done to improve the design of this experiment?
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15.10In
a classic study, which predates the existence of the EPO drug, Melvin Williams
of Old Dominion University actually injected extra oxygen-bearing red cells
into the subjects’ bloodstream just prior to a treadmill test. Twelve
long-distance runners were tested in 5-mile runs on treadmills. Essentially,
two running times were obtained for each athlete, once in the treatment or
blood-doped condition after the injection of two pints of blood and once in the
placebo control or non-blood-doped condition after the injection of a
comparable amount of a harmless red saline solution. The presentation of the
treatment and control conditions was counterbalanced, with half of the subjects
unknowingly receiving the treatment first, then the control, and the other half
receiving the conditions in reverse order.
Since the difference scores, as reported in the New York
Times,on May 4, 1980, are calculated by subtracting blood-doped
running times from control running times, a positive mean difference signifies
that the treatment has a facilitative effect, that is, the athletes’ running
times are shorter when blood doped. The 12 athletes had a mean difference
running time, D, of 51.33 seconds with a standard deviation, s
D, of 66.33 seconds.
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Question:
|
Calculations or Logic:
|
Answer:
|
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Test the
null hypothesis at the .05 level of significance.
|
Step 1
|
What is the research
problem?
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Step 2
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What is the null
hypothesis?
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What is the alternative
hypothesis?
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Step 3
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What is the decision
rule?
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Step 4
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What is the critical t?
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What is the value of t?
(you will need to calculate this)
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Step 5
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What is the decision?
(retain or reject the null hypothesis at the specified level of significance;
note the relationship between the observed and critical t scores)
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Step 6
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What is your
interpretation of the decision in relation to the original research problem?
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Specify
the p-value for this test result.
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Would you
have arrived at the same decision about the null hypothesis if the difference
scores had been reversed by subtracting the control times from the
blood-doped times?
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If
appropriate, construct and interpret a 95 percent confidence interval for the
true effect of blood doping.
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Calculate
Cohen’s dfor these results.
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Interpret
the effect size.
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How might
this result be reported in the literature?
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Why is it
important to counterbalance the presentation of blood-doped and control
conditions?
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Comment on
the wisdom of testing each subject twice—once under the blood-doped condition
and once under the control condition—during a single 24-hour period.
(Williams actually used much longer intervals in his study.)
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15.14In
Table 7.4 on page 173, all ten top hitters in the major league baseball in 2011
had lower batting averages in 2012, supporting regression toward the mean.
Treating averages as whole numbers (without decimal points) and subtracting
their batting averages for 2012 from those for 2011 (so that positive
difference scores support regression toward the mean), we have the following
ten difference scores: 14, 39, 61, 60, 13, 21, 50, 93, 16, 61.
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Question:
|
Calculations or Logic:
|
Answer:
|
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Test the
null hypothesis (that the hypothetical population mean difference equals zero
for all sets of top ten hitters over the years) at the .05 level of
significance.
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Step 1
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What is the research
problem?
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Step 2
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What is the null
hypothesis?
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What is the alternative
hypothesis?
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Step 3
|
What is the decision
rule?
|
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Step 4
|
What is the critical t?
|
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What is the value of t?
(you will need to calculate this)
|
|
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Step 5
|
What is the decision?
(retain or reject the null hypothesis at the specified level of significance;
note the relationship between the observed and critical t scores)
|
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Step 6
|
What is your
interpretation of the decision in relation to the original research problem?
|
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Specify
the p-value for this test result.
|
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Construct a
95% confidence interval.
|
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Calculate
Cohen’s d.
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How might
these findings be reported?
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