Homework 03

Homework 03 - 
 Homework
Assignment
3
...

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Unformatted text preview: 
 Homework
Assignment
3
 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. What
does
it
mean
for
a
sample
to
have
a
standard
deviation
of
zero?

Describe
the
scores
in
 such
a
sample.
 
 2. Explain
why
the
sum
of
squared
deviations,
SS,
can
not
ever
be
negative.
 
 
 3. Calculate
the
SS,
variance,
and
standard
deviation
for
the
following
population
of
6
scores:
 














































































11,
0,
8,
2,
4,
5
 a. SS
=

 b. Variance
=
 c. Standard
deviation
=

 
 4. Consider
a
sample
consisting
of
4
scores.
The
SS
for
this
sample
=
20.
 a. What
is
the
best
estimate
of
the
standard
deviation
of
the
population
from
which
this
 sample
is
drawn?
 b. What
is
the
standard
deviation
of
the
scores
in
this
particular
sample?
 
 5. The
following
sample
was
collected
with
the
explicit
purpose
of
determining
characteristics
 of
the
population
from
which
it
was
drawn.
Calculate
the
SS,
variance,
and
standard
 deviation
using
the
following
sample
of
n
=
4
scores:

 


















































































3,
1,
1,
1.
 a. SS
=

 b. Variance
=
 c. Standard
deviation
=

 
 
 6. A
distribution
has
a
standard
deviation
of
σ
=
8.
Find
the
z‐score
for
each
of
the
following
 locations
in
the
distribution.

 a. Above
the
mean
by
4
points
 b. Above
the
mean
by
16
points
 c. Below
the
mean
by
8
points
 d. Below
the
mean
by
12
points
 
 7. For
a
population
with
μ
=
50
and
σ
=
4
 a. Find
the
z‐score
for
each
of
the
following
X
values.

 i. X
=
55
 ii. X
=
60
 iii. X
=
35
 
 b. Find
the
score
(X‐value)
that
corresponds
to
each
of
the
following
z‐scores
 i. z
=
.80
 ii. z
=
‐0.50
 iii. z
=
0.30
 
 
 8. Find
the
z‐score
corresponding
to
a
score
of
X
=
60
for
each
of
the
following
distributions:
 a. μ
=
50,
σ
=
10
 b. μ
=
50,
σ
=
5
 
 
 9. A
score
that
is
6
points
below
the
mean
corresponds
to
a
z‐score
of
z
=
‐2.00.
What
is
the
 population
standard
deviation?

 
 
 10. For
a
population
with
a
standard
deviation
of
σ
=
10,
a
score
of
x
=
44
corresponds
to

 z
=
‐0.50.
What
is
the
population
mean,
μ?

 
 
 11. For
each
of
the
following
populations,
would
a
score
of
X
=
50
be
considered
a
central
score
 (near
the
middle
of
the
distribution)_
or
an
extreme
score
(far
out
in
the
tail
of
the
 distribution)?
 a. μ
=
45,
σ
=
10
 b. μ
=
40,
σ
=
2
 c. μ
=
51,
σ
=
2
 d. μ
=
60,
σ
=
20
 
 
 
 
 12. Which
of
the
following
exam
scores
should
lead
to
the
better
grade?
A
score
of
X
=
43
on
an
 exam
with
μ
=
40
and
σ
=
2,
or
a
score
of
X
=
60
on
an
exam
with
μ
=
50
and
σ
=
20?

Explain
 your
answer.
 13. Find
each
of
the
following
probabilities
for
a
normal
distribution:
 a. p(
z
>
‐0.80
)
 b. p(
z
<
0.25
)
 c. p(
z
>
‐2.10
)
 
 
 14. Find
each
of
the
following
probabilities
for
a
normal
distribution:
 a. p(
‐1.50
>
z
>
‐0.80
)
 b. p(
­1.00
<
z
<
0.25
)
 c. p(
‐2.00
<
z
<
1.25
)
 
 
 15. The
distribution
of
the
scores
on
the
SAT
is
approximately
normal
with
a
mean
of
μ
=
500
 and
a
standard
deviation
of
σ
=
100.
For
the
population
of
students
who
have
taken
the
SAT:
 a. What
proportion
have
SAT
scores
greater
than
700?
 b. What
proportion
have
SAT
scores
greater
than
550?
 c. What
is
the
minimum
SAT
score
needed
to
be
in
the
highest
10%
of
the
population?
 d. If
the
state
college
only
accepts
students
from
the
top
60%
of
the
SAT
distribution,
 what
is
the
minimum
SAT
score
needed
to
be
accepted?
 
 
 
 
 
 ...
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This note was uploaded on 10/16/2011 for the course PSYCH 60 taught by Professor Parris during the Spring '11 term at UCSD.

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