Midterm 1 - Version B - Short Answer

Midterm 1 - Version B - Short Answer -...

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









 
 VERSION
B
 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:
 40,
83,
60,
6,
18,
27

 a. Find
the
value
of
SS
for
this
sample.
Xbar
=
234/6
=
39

 
 
 
 
 X 40 83 60 6 18 27 X-Xbar 1 44 21 -33 -21 -12 (X-Xbar)2 1 1936 441 1089 441 144 












































Σ(X­Xbar)2

=

4052
 X 40 83 60 6 18 27 Σ = 234 
 Or




 
,



13178
–
2342/6
=
4052
 
 b. Assume
that
SS
=
4100
(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
(4100
/
5
)

 
 estimated
σ
=
sqroot
(
800
)

 estimated
σ
=
28.64
 
 
 
 X2 1600 6889 3600 36 324 729 Σ =13178 Psychology
60
–
Spring,
2010
–
Midterm1
–
Given
4/20/10
 2
 
 2) In
a
population
of
exam
scores,
a
score
of
X
=
90
corresponds
to
z
=
+2.00,
and
a
score
of
x
=
81
 corresponds
to
z
=
‐1.00.
Find
the
mean
and
standard
deviation
of
the
population.

 
 
 
 










μ
=

84





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
=
4.5,
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

=
4.5
+
(‐0.44)(1)
=
4.06
hours
 
 




















Xupper

=
4.5
+
(+0.44)(1)
=
4.94
hours
 
 
 
 
 
 
 
 

 
 ...
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