POL251_HW6(1)
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Dec 6, 2023
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POL 251: Introduction to Political Science Research Methods
Homework #6
Due Thursday, November 16 @ 2:30pm
(upload to the BlackBoard assignment, write all partner names on document)
Question 1:
Imagine a researcher wanted to know if the suicide rate (defined as the number of deaths due to
intentional self-harm per 100,000 population) differed between Southern states (ex: Alabama, Florida,
Georgia) and non-Southern states. The sample include N=16 Southern states, and N=35 non-Southern
states. The average suicide rate for Southern states is 14.7 and the average suicide rate for non-Southern
states is 15.8. There is
no
population information about the standard deviation, but the researchers know
that the sample standard deviations are s=2.4 for Southern states, and s=4.4 for non-Southern states.
Based upon this information, test the hypothesis that Southern states have a
different
suicide rate than non-
Southern states.
(1)
Is the proposed hypothesis
directional or non-directional
? Does it require a
one-tailed or two-tailed
statistical test?
(2)
If you wanted to create confidence intervals around the sample mean for Southern and non-Southern
states, would you use the standard normal (
Z
) distribution, or the student’s
t
distribution? Briefly
explain your answer.
(3)
Use the appropriate lookup table (Z or t based on your answer to part 2), to find the critical value with
α
= 0.05. Use either a one-tailed or two-tailed test as appropriate based upon your answer to part
1. Write down that critical value and show your work if appropriate. (Hint: If you choose the t
statistic, be sure to use use the appropriate degrees of freedom to find the critical value.)
(4)
Calculate each of the
standard errors
for Southern and non-Southern states’ samples. You should
calculate two different SE’s – one for Southern states, and one for non-Southern states. Use scrap
paper to show your work, and round answers to two decimal places. (Hint: SE =
s
/
√ n
)
(5)
Calculate each of the
95% confidence interval
for Southern and non-Southern states’ samples. You
should calculate two different CI’s – one for Southern states, and one for non-Southern states. Use
scrap paper to show your work, and round answers to two decimal places.
(Hint: C.I. = µ +/- Z*SE for
the standard normal distribution; C.I. = µ +/- t*SE for the t-distribution).
(6)
Based on your calculated 95% confidence intervals, do Southern states have a
different
suicide rate
than non-Southern states? Briefly explain why or why not.
1
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