Midterm 1 - Version A - Short Answer

Midterm 1 - Version A - Short Answer -...

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Unformatted text preview: Psychology
60
–
Spring,
2010
–
Midterm1
–
Given
4/20/10
 1
 
 Short
Answer
/
Computation
Questions:










 
 VERSION
A
 For
these
questions,
you
must
show
your
work
in
order
to
receive
any
credit.
If
you
are
using
a
 formula
to
solve
the
question,
write
the
formula
first,
and
then
apply
the
formula
to
the
problem.

 
 Write
legibly
and
CIRCLE
your
final
answer
for
each
question
 
 1) A
market
researcher
interested
in
how
much
individuals
on
the
UCSD
campus
talk
on
their
 phones
takes
a
sample
of
6
students
and
asks
them
to
report
how
many
minutes
a
day
they
 talk
on
their
phone.
The
following
are
the
data
this
researcher
obtains:
 39,
81,
59,
4,
18,
27

 a. Find
the
value
of
SS
for
this
sample.
Xbar
=
228/6
=
38
 
 
 
 
 X 39 81 59 4 18 27 X-Xbar 1 43 21 -34 -20 -11 (X-Xbar)2 1 1849 441 1156 400 121 












































Σ(X­Xbar)2

=

3968
 X 39 81 59 4 18 27 Σ = 228 
 Or




 
,



12632
–
2282/6
=
3968
 
 b. Assume
that
SS
=
4000
(DO
NOT
USE
ANY
OTHER
VALUE
FOR
SS).
 Find
the
best
estimate
of
the
standard
deviation
of
the
population.
 
 estimated
σ
=
sqroot(
SS/(n­1)
)
 
 estimated
σ
=
sqroot
(4000
/
5
)

 
 estimated
σ
=
sqroot
(
800
)

 estimated
σ
=
28.28
 
 
 
 X2 1521 6561 3481 16 324 729 Σ = 12632 Psychology
60
–
Spring,
2010
–
Midterm1
–
Given
4/20/10
 2
 
 
 2) In
a
population
of
exam
scores,
a
score
of
X
=
88
corresponds
to
z
=
+2.00,
and
a
score
of
x
=
79
 corresponds
to
z
=
‐1.00.
Find
the
mean
and
standard
deviation
of
the
population.

 
 
 
 






μ
=

82





σ
=
3

 
 
 
 
 
 
 
 
 
 
 3) A
research
firm
is
interested
in
obtaining
a
sample
of
individuals
who
use
Facebook
a
“typical
 amount
of
time
per
day,”
which
they
specifically
define
as
the
middle
34%
of
people
in
terms
 of
hours
spent
per
day
on
the
website.

Assume
that
Facebook
usage
in
terms
of
hours
per
day
 is
normally
distributed
with
μ
=
4.2,
and
σ
=
1.

Determine
the
cut‐off
values
in
number
of
 hours
per
day
that
this
research
firm
should
use
in
recruiting
subjects.

 
 
 
 









 














p(
‐0.44
<
Z
<
0.44
)
=
.34
 








 
 
 
 
 
 
 






Xlower

=
4.2
+
(‐0.44)(1)
=
3.76
hours
 
 




















Xupper

=
4.2
+
(+0.44)(1)
=
4.64
hours
 
 
 







 
 
 
 
 
 
 
 
 ...
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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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