lecture wk1

lecture wk1 - 4/1/10
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Unformatted text preview: 4/1/10
 •  Julian’s
Office
Hours
 –  Now
Wednesdays
from
2:00
‐
4:00
 •  StaAsAcs
as
a
discipline
 •  Terminology
 •  Use
of
staAsAcs
in
research
 –  Research
Methodologies
 –  Measurement
 1
 4/1/10
 Any
func%on
of
data
 •  ProporAon,
Sum,
Average,
Minimum,
Maximum
 •  Useful
to
represent
some
aspect
of
the
data
in
a
 simple,
easy
to
understand
way
 •  Is
defined
by
an
operaAon
on
data
 2
 4/1/10
 A
set
of
mathemaAcal
procedures
for
 organizing,
summarizing,
and
 interpreAng
informaAon
 •  Prac%cal
math
 •  DescripAve:
staAsAcal
procedures
to
 summarize,
organize,
and
simplify
data
 •  InferenAal:
staAsAcal
techniques
that
facilitate
 inferences
from
samples
to
populaAons
 Obama
received
53.4%
 of
the
vote
in
the
2008
 PresidenAal
ElecAon
 66,882,230
votes
out
of
 125,225,901
votes
 Obama
is
predicted
to
 receive
55%
of
the
vote
in
 the
2008
PresidenAal
 ElecAon,
±2.1%
 Gallup
Poll
of
2472
voters,

11/2/08
 3
 4/1/10
 •  Data
(plural)
are
measurements
or
 observaAons
 •  Data
set:
collecAon
of
measurements
or
 observaAons
 •  Datum
(singular):
is
a
single
measurement
or
 observaAon,
aka.
Score,
or
raw
score
 a
characterisAc
or
condiAon
that
changes
or
 has
different
values
for
different
individuals

 •  Age,
Gender,
Height,
Facebook
user
or
not
 4
 4/1/10
 A
populaAon
is
the
set
of
all

 individuals
(units)
of
interest

 A
sample
is
a
set
of
individuals
(units)
 selected
from
a
populaAon
 •  Plankton
in
the
ocean,
People
in
the
world,
 People
at
UCSD,
Dogs
in
San
Diego
 –  Usually
intended
to
“represent”
the
populaAon
 –  Usually
much
smaller
than
populaAon
 PopulaAon
 Sample
 Average
 Sum
 Maximum
score
 •  Parameter:
a
value
 (usually
numeric)
 that
describes
a
 populaAon
 •  StaAsAc:
a
value
 (usually
numeric)
 that
describes
a
 sample
 Average
 Sum
 Maximum
score
 STATISTICS
 PARAMETERS
 5
 4/1/10
 PopulaAon
 260‐
Psych
60
 students
 PopulaAon
Parameters
 Average
Age:
19.8
 Average
IQ:
110.5
 70%
Female,
30%
Male
 Sample
2
 Jake
 Laura
 Tiffany
 Sarah
 Ann
 Sample
1
 Mike
 Tom
 Jennifer
 Andy
 Lucy
 Sample
1
Sta%s%cs
 Average
Age:
21.8
 Average
IQ:
106.2
 40%
Female,
60%
Male
 Sample
2
Sta%s%cs
 Average
Age:
19.2
 Average
IQ:
112.2
 80%
Female,
20%
Male
 PopulaAon
Parameters
 Average
Age:
19.8
 Average
IQ:
110.5
 70%
Female,
30%
Male
 Sample
1
Sta%s%cs
 Average
Age:
21.8
 Average
IQ:
106.2
 40%
Female,
60%
Male
 Sample
2
Sta%s%cs
 Average
Age:
19.2
 Average
IQ:
112.2
 80%
Female,
20%
Male
 PopulaAon
 All
UCSD
 Students
 The
discrepancy
(or
amount
of
error)
that
 exists
between
a
sample
staAsAc
and
the
 corresponding
populaAon
parameter
 No
Caffeine
Group
 Group
2
Sta%s%cs
 n
=
50
 82,
77
79,
 Average
test
score:
79
 64,
81,
92,
 74,
88,
91,
 81,
79,
70...
 Caffeine
Group
 n
=
50
 86,
76,
89,
 91,
78,
89,
 67,
54,
67,
 88,
75,
90...
 Group
1
Sta%s%cs
 Average
test
score:
75
 6
 4/1/10
 Check
Your
Understanding
 A
researcher
is
interested
in
the
effect
of
amount
of
 sleep
on
high
school
students’
exam
scores.
A
group
 of
75
high
school
boys
agree
to
parAcipatein
the
 study.
The
boys
are…

 A
 B
 C
 D
 E
 •  A
staAsAc
 •  A
variable
 •  A
parameter
 •  A
sample
 •  A
populaAon
 Check
Your
Understanding
 A
researcher
is
interested
in
the
effect
of
amount
of
 sleep
on
high
school
students’
exam
scores.
A
group
 of
75
high
school
boys
agree
to
parAcipate
in
the
 study.
The
boys
are…

 Check
Your
Understanding
 A
researcher
measured
40
children
on
a
vocabulary
 test,
20
of
whom
were
homeschooled
and
20
of
 whom
went
to
public
schools.
The
homeschooled
 children
knew
on
average
10
more
words.
True
or
 false:
this
difference
of
ten
words
means
that
 homeschooled
children
in
general
know
more
 words
than
children
in
public
schools.
 A
 B
 C
 D
 E
 •  A
staAsAc
 •  A
variable
 •  A
parameter
 •  A
sample
 •  A
populaAon
 A
 B
 •  True
 •  False
 7
 4/1/10
 Check
Your
Understanding
 A
researcher
measured
40
children
on
a
vocabulary
 test,
20
of
whom
were
homeschooled
and
20
of
 whom
went
to
public
schools.
The
homeschooled
 children
knew
on
average
10
more
words.
True
or
 false:
this
difference
of
ten
words
means
that
 homeschooled
children
in
general
know
more
 words
than
children
in
public
schools.
 A
 B
 •  True
 •  False
 •  StaAsAcs
as
a
discipline
 •  Terminology
 •  Use
of
staAsAcs
in
research
 –  Research
Methodologies
 –  Measurement
 8
 4/1/10
 Two
variables
are
observed
to
determine
 if
there
is
a
relaAonship
between
them

 Murders
 Ice
Cream
Sales
 9
 4/1/10
 10
 4/1/10
 •  “cum
hoc
ergo
propter
hoc”
 
(with
this,
therefore
because
of
this)
 •  “CorrelaAon
does
not
imply
causaAon”
 11
 4/1/10
 Sample
1
 n
=
5
 Hanger
 Sample
2
 n
=
5
 Access
Logs
 Record
 Speed
&
 VibraAon
 Record
 Speed
&
 VibraAon
 =
650
miles/hour
 Access
Logs
 =
590
miles/hour
 12
 4/1/10
 Randomly
Assign
 Manipulate
 Independent
Variable
 Measure

 Dependent
Variable
 Sample
1
 n
=
5
 Hanger
 Sample
2
 n
=
5
 Run
Test
in
Tunnel
 Measure
 Speed
 Measure
 Speed
 =
stable
at
600
miles/hour
 Run
Test
in
Tunnel
 =
stable
at
600
miles/hour
 Control
Extraneous
 Variables
 •  ManipulaAon:
manipulaAng
independent
 variable
to
see
the
effect
it
has
on
the
 dependent
variable
 •  Control:
ensure
that
extraneous
variables
are
 constant
across
the
levels
of
the
independent
 variable
 •  Random
Assignment:
chance
alone
dictates
 which
individual
is
in
each
condiAon
 13
 4/1/10
 •  StaAsAcs
as
a
discipline
 •  Terminology
 •  Use
of
staAsAcs
in
research
 –  Research
Methodologies
 –  Measurement
 Internal
aoributes
or
characterisAcs
that
 cannot
be
directly
observed

 14
 4/1/10
 A
procedure
for
measuring
an
external
 behavior
so
that
those
measurements
may
 be
used
to
infer
about
the
status
of
the
 underlying
construct
 15
 4/1/10
 •  Discrete
variables
consists
of
separate
 categories
where
no
values
exist
between
 neighboring
categories
 •  ConAnuous
variables
have
an
infinite
number
 of
values
fall
between
any
two
observed
 values

 a
nominal
scale
 consists
of
a
set
 of
categories
that
 have
different
 names.

 an
ordinal
scale
 consists
of
a
set
of
 categories
that
 are
organized
in
 an
ordered
 sequence
 e.g.
finishing
place
 in
race,
Clothing
 sizes
(S,M,L,XL)
 Olympic
medals

 an
interval
scale
 consists
of
a
series
 of
ordered
 categories
where
 the
categories
form
 intervals
of
the
 same
size
 e.g.
distance,
 weight,
 temperature
 Scale
 Nominal
 Ordinal
 Interval
 Ra;o
 Labels
for
 observa.ons
 Ordered
 Categories
 Equal
 Intervals
 Meaningful
 Zero
point
 X
 X
 X
 X
 X
 X
 X
 X
 X
 X
 e.g.
gender,
 poli%cal
ideology

 16
 4/1/10
 Check
Your
Understanding
 A
researcher
measures
“mood”
as
“the
number
of
 nights
an
individual
sees
his
or
her
friends
in
a
given
 month”
 On
what
scale
is
“mood”
measured?
 A
 B
 C
 •  Nominal
Scale
 •  Ordinal
Scale
 •  Interval/RaAo
Scale
 Check
Your
Understanding
 A
researcher
measures
“mood”
as
“the
number
of
 nights
an
individual
sees
his
or
her
friends
in
a
given
 month”
 On
what
scale
is
“mood”
measured?
 Check
Your
Understanding
 Is
the
variable
“mood”
discrete
or
conAnuous?
 A
 B
 C
 •  Nominal
Scale
 •  Ordinal
Scale
 •  Interval/RaAo
Scale
 A
 B
 •  Discrete
 •  ConAnuous
 17
 4/1/10
 Check
Your
Understanding
 Is
the
variable
“mood”
discrete
or
conAnuous?
 A
 B
 •  Discrete
 •  ConAnuous
 •  Read
 –  Syllabus
 –  Chapters
1
and
2
 •  Do
 –  Buy
Clicker
 –  Buy
Book
 –  Homework
1
(due
Tuesday
by
start
of
class)
 18
 ...
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