psych60 hw

psych60 hw - 
 Homework
Assignment
5
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Unformatted text preview: 
 Homework
Assignment
5
 Psychology
60
 Spring
2010
 
 
 
 General
Instructions:
 ‐ Make
sure
your
homework
has
written
on
it:
 o YOUR
NAME
 o YOUR
STUDENT
ID
 o YOUR
TA’S
NAME
(you
can
find
this
on
the
syllabus)
 
 ‐ Please
be
sure
your
homework
answers
are
LEGIBLE.
 
 ‐ For
homework
problems
requiring
calculation,
you
must
show
all
of
your
work,
 including
intermediate
steps,
in
order
to
receive
credit.


 ‐ Please
circle
final
answers
to
problems
that
require
computation;
doing
this
will
make
sure
 we
can
find
your
final
answer.

 ‐ For
questions
requiring
a
short
written
answer,
be
as
concise
as
possible
while
still
 explaining
your
answer.

 
 ‐ If
you
have
questions
about
concepts,
feel
free
to
post
questions
on
the
class
discussion
 board.
You
may
also
email
your
TAs,
but
do
so
only
after
you
have
looked
through
the
book
 for
an
answer
to
your
question.

 ‐ Homework
is
due
at
the
start
of
class
on
Tuesday
(by
11:15).
No
late
homework
will
be
 accepted.
 
 
 1) The
value
of
 z X in
a
hypothesis
test
is
influenced
by
a
variety
of
factors.
Assuming
that
all
 other
variables
are
held
constant,
explain
how
the
value
of
 z X 
is
influenced
by
each
of
the
 following:
 a. Increasing
the
difference
between
the
sample
mean
 X 
and
the
untreated
population
 mean
μ
(the
mean
given
H0:
True)
 b. Increasing
the
population
standard
deviation,
σ
 c. Increasing
the
number
of
scores
in
the
sample,
n
 
 2) A
researcher
is
investigating
the
effectiveness
of
a
new
study‐skills
training
program
for
 elementary
school
children.
A
sample
of
n
=
25
third‐grade
children
is
selected
to
participate
 in
the
program
and
each
child
is
given
a
standardized
achievement
test
at
the
end
of
the
 year.
For
the
regular
population
of
third‐grade
children,
scores
on
the
test
form
a
normal
 distribution
with
mean
of
μ
=
150
and
a
standard
deviation
of
σ
=
25.
The
mean
for
the
 sample
is
 X 
=
158.
Assuming
a
non‐directional
(two
tailed)
hypothesis,
with
 α =0.05:
 a. Identify
the
independent
and
dependent
variables
 b. In
a
sentence,
state
the
null
hypothesis
being
tested
 c. In
symbols,
state
the
null
hypothesis
and
the
alternative
hypothesis
 d. Identify
the
critical
values
of
 z X .
That
is,
beyond
what
values
will
you
reject
the
null
 hypothesis?
 e. Calculate
 z X 
for
the
sample
mean
 f. What
decision
should
be
made
about
the
null
hypothesis
and
the
effectiveness
of
this
 study‐skills
program?
 
 
 3) If
the
alpha
level
of
a
study
is
changed
from
 α =0.05
to
 α =0.01,
 a. What
happens
to
the
boundaries
of
the
critical
region?

 (report
the
actual
critical
values
for
each
 α =0.05
and
 α =0.01)
 b. What
happens
to
the
probability
of
a
Type
I
error?
 (report
the
actual
probability
of
a
Type
I
error
for
each
 α =0.05
and
 α =0.01)
 c. What
happens
to
the
probability
of
a
Type
II
error
given
H1
is
true?
 (report
­in
general­
what
happens
to
the
probability
of
a
Type
II
error)
 
 
 4) Imagine
San
Diego
State
is
evaluating
a
new
English
composition
course
for
freshmen.
A
 random
sample
of
n
=
25
freshmen
is
obtained
andthe
students
are
placed
in
the
course
 during
their
first
semester.
One
year
later,
a
writing
sample
is
obtained
for
each
student
and
 the
wiring
samples
are
graded
using
a
standardized
evaluation
technique.
The
mean
score
 for
the
sample
is
 X =76.
For
the
general
population
of
college
students,
writing
scores
form
a
 normal
distribution
with
a
mean
of
μ
=
70.
 a. If
the
writing
scores
for
the
population
have
a
standard
deviation
of
σ
=
20,
does
the
 sample
provide
enough
evidence
to
conclude
that
the
new
composition
course
has
a
 statistically
significant
effect?
Assume
a
two‐tailed
test
with
 α =0.05.
 b. If
the
writing
scores
for
the
population
have
a
standard
deviation
of
σ
=
10,
does
the
 sample
provide
enough
evidence
to
conclude
that
the
new
composition
course
has
a
 statistically
significant
effect?
Assume
a
two‐tailed
test
with
 α =0.05.
 c. Comparing
your
answers
in
part
a
and
part
b,
explain
how
the
magnitude
of
the
 standard
deviation
influences
the
outcomes
of
a
hypothesis
test.
 
 
 5) A
researcher
is
evaluating
the
influence
of
a
treatment
using
a
random
sample
selected
from
 a
normally
distribution
population
with
a
mean
of
μ
=
80
and
a
standard
deviation
of
σ
=
20.
 The
researcher
expects
a
12‐point
treatment
effect
and
plans
to
use
a
two‐tailed
hypothesis
 test
with
 α =0.05.
 a. Calculate
Cohen’s
d
for
this
effect.
How
large
(in
words)
is
this
effect
using
the
general
 guidelines
given
by
Cohen?
 b. Compute
the
power
of
the
hypothesis
test
if
the
researcher
uses
a
sample
size
of
n
=
 16
individuals
 c. Compute
the
power
of
the
hypothesis
test
if
the
researcher
uses
a
sample
size
of
n
=
 25
individuals.
 ...
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