Homework 02 - Answers and Points

Homework 02 - Answers and Points - 
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Unformatted text preview: 
 Homework
Assignment
2
 
 
 
 
 Psychology
60
 Spring
2010
 1. (4
points
total)

Use
summation
notation
to
express
each
of
the
following
calculations:
 a. (1
point)
Square
each
score,
then
add
the
squared
values.
 ΣXi2 or Σ( Xi2 ) or ΣX 2 or Σ( X 2 ) 
 b. (1
point)
Add
the
scores,
then
square
the
sum.
 ( ΣXi )2 or ( ΣX )2 
 c. (1
point)
Add
two
points
to
each
score,
then
add
the
resulting
values.
 Σ( Xi + 2 ) or Σ( X + 2 ) 
 d. (1
point)
Add
the
scores,
then
subtract
6
points
from
the
total.
 ( ΣXi ) − 6 or ( ΣX ) − 6 or ΣXi − 6 or ΣX − 6 
 
 2. (3
points)
Construct
a
grouped
frequency
distribution
table
to
organize
the
following
set
of
 scores,
which
range
from
88
to
470.
 319,

 241,

 104,
 165,

 97,

 452,

 280,
 
 88,
 225,
 396,
 271,
 233,
 470,
 356,
 159,
 266,
 112,
 293,
 174,
 268,
 153
 

 
 X
 
 f
 
 450­499
 2
 
 400­449
 0
 
 350­399
 2











note:
several
ways
to
do
this.
Full
points
if
there
are

 
 300­349
 1
 
about
10
classes
of
equal
spacing
without
any
bins

 
 250­299
 5
 
omitted
 
 200­249
 3
 
 150­199
 4
 
 100­149
 2
 50­99
 
 2
 
 3. (3
points)
Line
charts
are
sometimes
used
incorrectly
to
display
data
that
should
be
 presented
in
a
bar
chart.
For
example,
the
following
line
chart
is
an
incorrect
way
to
show
 the
average
GPA
in
five
different
majors
at
UCSD.
Explain
in
your
own
words
why
a
line
chart
 is
inappropriate
for
data
such
as
these.


 
 For
these
data
it
is
inappropriate
to
use
a
line
chart.
Line
charts
 should
not
be
used
when
the
x
axis
is
nominally
scaled.
The
 reason
is
that
using
a
line
chart
here
implies
that
there
is
some
 sensible
point
between
the
categories
on
the
x
axis.
Because
the
 categories
on
the
x
axis
are
college
majors
(a
nominal
scale)
and
 they’re
not
ordered
in
some
way
that
represents
an
underlying
 continuous
scale,
it
is
not
appropriate
to
have
a
line
connecting
 the
categories.

A
bar
graph
is
the
appropriate
chart.


 
 4. (3
points)
Come
up
with
a
hypothetical
data
example
in
which
the
use
of
a
scatter
plot
 would
be
a
correct
way
to
visualize
data.
You
do
not
need
to
produce
hypothetical
data,
only
 a
situation
and
the
names
of
the
variables
you
would
measure.

 For
full
credit
the
answer
must
have
two
variables
that
are
both
measured
on
 an
interval
or
ratio
scale
and
can
be
measured
from
the
same
unit.

For
 example,
individuals’
heights
and
weights.
Both
of
these
variables
are
ratio
 scale,
and
both
can
be
obtained
from
the
same
individual.

 
 5. 
(3
points)
Sketch
a
histogram
showing
the
distribution
of
scores
presented
in
the
following
 table:
 
 
 X
 5
 4
 3
 2
 1
 
 
 
 
 
 
 f
 1
 5
 6
 3
 2
 
 6. (3
points)
An
instructor
at
the
state
college
recorded
the
academic
major
for
each
student
in
 a
psychology
class.
Construct
a
frequency
distribution
table
for
the
following
results:
 
 
 
 
 
 
 
 
 Psych
 
 Heath
 
 Soc
 
 Hist
 
 Nurs
 
 
 
 Bio
 
 Phys
Ed
 Health

 Psych
 
 Soc
 
 
 
 
 
 
 
 
 
 
 
 
 Soc
 Psych
 
 Psych
 
 Art
 
 Psych
 
 Engl
 
 Art
 
 Phys
Ed
 Health

 Psych
 
 Psych
 Psych
 Soc
 Psych
 Pol
Sci
 
X
 
 f
 _______________________
 ART
 
 2
 BIO
 
 1
 ENGL
 
 1
 HEALTH
 3
 HIST
 
 1
 NURS
 
 1
 PHYS
ED
 2
 POL
SCI
 1
 PSYCH
 9
 SOC
 
 4
 
 Other
orders
are
fine,
as
well.

 
 
 
 
 
 7. (2
points)
A
population
of
N
=
25
scores
has
a
mean,
μ
=
10.

What
is
the
value
of
∑Xi
for
this
 population?
 
 ΣXi ΣXi µ= , 10 = , ∴ ΣXi = 250 








(note
∴ means
“therefore”)
 N 25 
 8. (4
points
total)
Does
it
ever
seem
to
you
that
the
weather
is
nice
during
the
work
week,
but
 lousy
on
the
weekend?

Cerveny
and
Balling
(1988)
have
confirmed
that
this
is
not
your
 imagination
–
pollution
accumulating
during
the
work
week
most
likely
spoils
the
weekend
 weather
for
people
on
the
Atlantic
coast.

Consider
the
following
hypothetical
data
showing
 the
daily
amount
of
rainfall
for
10
weeks
during
the
summer.
 Week
 Av.
Daily
Rainfall
 Weekdays
(M
–
F)
 Av.
Daily
Rainfall
 Weekends
(Sat.
/
Sun.)
 1
 1.2
 1.5
 2
 0.6
 2.0
 3
 0.0
 1.8
 4
 1.6
 1.5
 5
 2.4
 0.2
 0.8
 8
 0.9
 1.6
 9
 1.1
 1.2
 10
 
 
 2.1
 7
 
 2.2
 6
 
 0.8
 1.4
 1.7
 
 a. (3
points,
‐‐
1.5
for
each
mean‐‐)
Calculate
the
average
daily
rainfall
(the
mean)
during
 the
week,
and
the
average
daily
rainfall
for
the
weekends.
 
 ΣXi 9.9 Xweek = , Xweek = , ∴ Xweek = 0.99 
 n 10 
 ΣXi 16.7 Xweekend = , Xweekend = , ∴ Xweekend = 1.67 
 n 10 b. (1
point)
Based
on
the
two
means,
does
there
appear
to
be
a
pattern
in
the
data?
 Yes,
there
is
a
mean
difference
between
these
samples;
it
rained
more
on
the
 weekends
sampled
than
the
weekdays
sampled.

 
 (note:
need
to
do
more
work
before
we
can
conclude
that
this
is
good
evidence
 for
a
true
difference
rather
than
just
sampling
error)

 
 9. (3
points
–1
for
each
measure
of
central
tendency‐‐)
Find
mean,
median,
and
mode
for
the
 following
sample
of
scores:
 7,
5,
9,
7,
7,
8,
6,
8,
10,
7,
4,
6
 ΣXi 84 , X= , ∴ X = 7
 n 12 
 
 Mean:
 X = 
 
 
 Median:

 Step
1
(Order
scores):
4,
5,
6,
6,
7,
7,
7,
7,
8,
8,
9,
10

 Step
2
(find
middle
two
scores,
N/2,
N/2
+1):


7,
7
 Step
3
(find
mean
of
middle
two
scores):
(7+7)
/
2
=7
 Median
=
7
 
 
 
 Mode
(most
common
score):
7
 ...
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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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