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assignmentchapter7and8.docxChapter 7: Single-sample t Test
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1
One of the differences between a z for a sample mean test and a single sample t test is that:
A
the z for a sample mean is used when you do not know the population standard deviation
B
the single sample t test uses the sample standard deviation to compute an estimate of the typical amount of sampling error.
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2
A researcher wants to assess people’s knowledge of a topic by using a 10-question True/False test. Which value could be of theoretical interest to this researcher and, therefore, function as a null hypothesis test value?
A
The researcher might compare the mean number of correct answers to 10, the number that represents perfect performance on the test.
B
The researcher might compare the mean number of correct answers to 5, the average number of correct answers people would get if they were simply guessing on every question of the test.
C
The researcher could use either “10” or “5” in this situation because both values represent a level of performance that might be of theoretical interest to the researcher
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3
The only computational difference between the z for a sample mean formula and the single sample t formula is the way:
A
the numerator is computed
B
typical sampling error is computed.
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5
The critical value for a one-tailed t test with α = .05:
A
is the same as the critical value for a similar z test.
B
changes based on the size of the sample (i.e., N) being used.
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6
The critical value for a t test will get ______ as sample size increases
A
farther from zero
B
closer to zero
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7
As the sample size increases, the critical region for a t test:
A
gets larger (more than 5% of the distribution).
B
gets smaller (less than 5% of the distribution).
C
stays the same size (equal to 5% of the distribution), but its location changes.
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8
When performing a t test, increasing the sample size will ______ the amount of sampling error expected. This means the denominator of the t test will be ________.
A
increase; smaller
B
increase; larger
C
decrease; smaller
D
decrease; larger
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9
You use a single sample t when:
A
the IV defines two independent samples and the DV is measured on an interval/ratio scale.
B
the IV defines two matched samples and the DV is measured on an interval/ratio scale.
C
the IV defines one sample, the DV is measured on an interval/ratio scale, and the DV is measured twice on that same sample.
D
the IV defines one sample and the DV is measured on an interval/ratio scale and you do not know the population standard deviation.
E
the IV defines one sample and the DV is measured on an interval/ratio scale and you do know the population standard deviation
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10
When performing a single sample t test, which of the following assumptions is the most difficult to assess?
A
Data independence
B
Appropriate measurement of the IV and DV
C
Normality of the distribution of sample means
D
Homogeneity of variance
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11
One-tailed significance tests:
A
have one critical region that is either on the positive or negative side of a distribution.
B
have two critical regions one on the positive side and one on the negative side of a distribution.
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12
When using a one-tailed significance test, if the research hypothesis predicts an increase (or positive change), the critical region will be on the ______ side of the distribution.
A
negative
B
positive
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13
The degrees of freedom (df) for a single sample t test are computed as:
A
N
B
N-1
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14
The degrees of freedom are used to:
A
compute the single sample t.
B
determine the critical value.
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15
If the research hypothesis indicates that scores will decrease, the critical value will be:
A
positive
B
negative
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16
For this example, the observed difference between the sample mean and the population mean was ______; the difference expected due to sampling error was ______.
A
268.186; 680
B
680; 268.186
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17
If the obtained t value is further from zero than the critical value, you should:
A
reject the null hypothesis
B
fail to reject the null hypothesis
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18
When computing an effect size for a single sample t test, the denominator is:
A
the sample standard deviation
B
the population standard deviation.
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19
The number in the parentheses in the character string “t (14) = 2.22, p < .05, d = .57” is the:
A
number of participants in the study.
B
degrees of freedom
C
critical t value.
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20
Generally, you should report ______, but it is acceptable to report ______ when you are computing your statistical tests by hand.
A
p > .05 or p < .05; exact p values
B
exact p values; p > .05 or p < .05
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21
Why is your decision to conduct a one-tailed rather than a two-tailed test potentially important?
A
One- and two-tailed tests have different critical regions and therefore may lead to different conclusions about the null hypothesis.
B
One- and two-tailed tests will produce different obtained t values.
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22
When should you conduct a one-tailed test?
A
A one-tailed test should be conducted when the research hypothesis predicts scores will increase or if it predicts scores will decrease.
B
A one-tailed test should be conducted when the research hypothesis does not specify if scores will increase or decrease.
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23
Which of the following symbols should be used to represent a two-tailed research hypothesis?
A
≤
B
>
C
=
D
≠
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25
Which of the following alpha values creates a greater probability of a Type I error?
A
.01
B
.05
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26
Which of the following alpha values creates a greater probability of a Type II error?
A
.01
B
.05
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27
Which of the following alpha values results in more statistical power?
A
.01
B
.05
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Chapter 8: Confidence Intervals
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1
Significance tests (e.g., single sample t tests) were designed to help researchers determine if the observed difference was likely to be created by:
A
sampling error.
B
confounds.
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2
If a statistical test leads to rejecting the null hypothesis, the research finding is always important or useful
A
True
B
False
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3
An effect size can help a researcher determine:
A
if an effect is large enough to be useful.
B
if the mean difference is likely to be due to sampling error.
C
both of the above.
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4
The purpose of a confidence interval is to:
A
test for significant differences.
B
quantify the effectiveness of a treatment.
C
help researchers estimate a population parameter with a specific level of confidence and precision.
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5
Confidence intervals provide researchers with:
A
a range of plausible values for a population parameter.
B
information that helps apply results from samples to populations.
C
both of the above.
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6
Which of the following might be used as a point estimate in a confidence interval?
A
Upper bound
B
Lower bound
C
Sample mean
D
Margin of error
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7
The size of the range of plausible parameter values provided by a confidence interval is determined by the:
A
sample mean
B
margin of error
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8
Which of the following contribute to the size (i.e., width) of the margin of error? (Choose two)
Multiple answers:You can select more than one option
A
Sample mean
B
Confidence level (95% vs. 99%)
C
Expected sampling error
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9
In general, 99% confidence intervals are _____ than 95% confidence intervals.
A
wider
B
narrower
C
more precise
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10
When creating a 95% CI, use a critical t value from the:
A
two-tailed .01 t table
B
two-tailed .05 t table.
C
one-tailed .01 t table.
D
one-tailed .05 t table.
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11
Which of the following determine the correct tCI score for a given CI? (Choose 2)
Multiple answers:You can select more than one option
A
Confidence levels (e.g. 95% or 99%)
B
The df
C
Expected sampling error
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12
In the above example, the upper and lower CI boundaries represent:
A
the highest and lowest values for the population parameter that are considered plausible, or reasonable considering sampling error.
B
the effect size from the study
C
the probability of rejecting the null hypothesis.
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13
When computing a CI for a mean difference, if zero is found to be a plausible value (i.e., it is between the upper and lower boundaries), a two-tailed significance test would find that the two means are:
A
NOT significantly different
B
significantly different
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14
Which of the following determines plausible values for population parameters?
A
Significance testing
B
Effect sizes
C
Confidence intervals
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15
The APA Manual recommends that researchers use:
A
CIs rather than significance testing.
B
CIs in conjunction with significance testing and effect sizes.
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16
Which of the following is NOT a correct interpretation of a 95% CI?
A
A range of plausible parameter values.
B
A wider CI is less precise than a narrow CI.
C
A 95% CI of [15, 30] means that 95% of the time replications of that study will produce a sample mean between 15 and 30.
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17
If the value of zero is NOT included between the upper and lower boundaries of a 95% CI for a mean difference, the two means used to create the point estimate are?
A
Not significantly different.
B
significantly different.
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