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Stats 250  Fall 2010 – Sunday Exam 2 Review  SOLUTIONS
Page 1
1  Cyberbullying –
involves the use of communication technologies to support deliberate, repeated, and hostile
behavior by an individual or group, that is intended to harm others.
A recent study of 200 high school males and
400 high school females resulted in 20% of the males and 26% of the females reporting they have been victims of
cyberbullying.
Assume these study results come from independent random samples.
You are asked to use these
results to test the theory that high school females are cyberbullied more than high school males, at the 5% level, i.e,
Ho:
p
1
=
p
2
vs Ha:
p
1
<
p
2
,
a.
Here, p
1
= the proportion for the population of high school males who have been victims of cyberbullying.
b.
Suppose the resulting test statistic is z = 1.6 and the corresponding
p
value is 0.055. Consider the following
statements and determine which are true regarding this study.
•
The results are statistically significant at the 5% level.
•
At the 5% level, the cyberbullying rate for high school females does not appear to be higher than
that for high school males.
•
The probability that the null hypothesis is true is estimated to be 5.5%.
•
The cyberbullying rate for the sampled high school males was 1.6 (null) standard errors below the
cyberbullying rate for the sampled high school females.
•
One condition for this test to be valid is that the models for the response for each population is
normal.
2  Grading Papers –
Suppose Jane is curious about the factors that influence paper grading by professors. She has a
hunch that papers that are typed are rated higher than papers that are handwritten on average.
To test her hunch she
conducted a study.
A total of 43 freshman students are currently taking an English class and 20 of the students wrote
their latest paper by hand, while the other 23 students typed their latest paper. All submitted papers were graded by the
professor who teaches the English class.
Jane obtained the scores from the professor and whether the paper had been
written by hand or typed.
She entered the data into SPSS and the following output was obtained.
A 5% significance
level
will
be
used
and
you
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This note was uploaded on 12/10/2010 for the course STATS 250 taught by Professor Gunderson during the Fall '10 term at University of Michigan.
 Fall '10
 Gunderson
 Statistics

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