PSYCH 240A
:
EXAM THREE
November 10, 2008
1.
Given the following data: M = 94,
μ
0
= 90, s = 10, n = 25
Calculate the tscore for this data and decide whether you should reject or accept the null
hypothesis. (Cutoff Value t
(24)
= 2.064).
a.
t = 2.5, reject the null hypothesis
b.
t = 2.5, accept the null hypothesis
c.
t = 2.0, reject the null hypothesis
d.
t = 2.0, accept the null hypothesis
2.
When estimating the population variance from a sample of scores, which of the following is an
unbiased estimator of the variance?
a.
[
Σ
(XM)
2
/ N]
b.
[
Σ
(XM)
2
/ (N Ð 1)]
c.
Σ
(XM)
2
/ N
d.
Σ
(XM)
2
/ (N Ð 1)
3.
What is the difference between a ttest for a single sample and a ttest for dependent means?
a.
In a single sample, there is one score for each subject, but for dependent means, there are 2
scores for each subject
b.
In a single sample, the sample mean is compared to the known population mean, but in
dependent samples, the sample mean is compared to an unknown population mean.
c.
The test for dependent means cannot be done on a computer.
d.
In a single sample, there is one score for each subject, but for dependent means, there is one
score for every two subjects.
For the next two questions, decide whether a ttest for a single sample or a ttest for dependent
means should be performed.
4.
A professor wants to determine whether SAT test scores from a sample of 25 undergraduate
students in her class are different from the national average (i.e. the population). The students in
her class have an average SAT score of 1200, with a standard deviation of 200. The national
average is 1100. She should use
a.
Unable to Determine
b.
Either test will work
c.
tTest for Dependent Means
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 Spring '08
 HARVEY
 Psychology, Standard Deviation, Variance, Null hypothesis, Single Sample, independent means

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