Homework #3
Extra Problems
1.
What is the difference between a distribution and a sampling distribution?
2.
In the zscore formula as it is used in a hypothesis test, explain
a.
what is measured by
μ

X
in the numerator.
b.
what is measured by the σ in the denominator.
c.
why you divide

X
by σ to get Z.
3.
On a standardized anagram task, people successfully complete an average of μ=26 anagrams
and σ=4. This distribution is normal. A researcher would like to demonstrate that the arousal
from anxiety is distracting and will decrease task performance.
A sample of n=14 anxiety
ridden subjects is tested on the task. The average number of anagrams solved is
X
= 23.36.
a.
Do the anxietyridden subjects show a decrease in task performance? Test with alpha
set at .01 for one tail.
b.
If a twotailed test with an alpha of .01 was used, what conclusion should be drawn?
c.
What does this demonstrate about onetailed versus twotailed tests?
4.
After several years of studying human performance in flight simulators, a psychologist
knows that reaction times to an overhead emergency indicator form a normal distribution
with μ=200 milliseconds and σ=20.
The psychologist would like to determine if placing the
indicator in front of the person at eye level has any effect on reaction time.
A random sample
of n=25 is selected, they are tested in a simulator with the indicator light at eye level, and
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 Spring '10
 allen
 Standard Deviation, Null hypothesis, Statistical hypothesis testing, Type I and type II errors, Statistical power

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