monfils 418_hypothesis testing2-2014

87therefore h0387 h1387 step2setcricalregion alpha05

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Unformatted text preview: violent
videos
leads
to
an
 increase
in
the
number
of
aggressive
words.

 What
if
σ
is
Not
Known?
 •  Assume
same
example,
but
σ
not
known
 •  We
can’t
simply
subs$tute
s
for
σ,
and
use
the
 z
distribu$on
 What
if
σ
is
Not
Known?
 •  Assume
same
example,
but
σ
not
known
 •  We
can’t
simply
subs$tute
s
for
σ,
and
use
the
 z
distribu$on
 •  Instead,
we
subs$tute
s
for
σ,
but
we
call
the
 answer
t, and
use
a
different
distribu$on!
 •  Compare
t 
to
tabled
values
of
t instead
of
to
 distribu$on
of
z
 t
Test
for
One
Mean
 •  Same
as
z,
except
for
s
in
place
of
σ

 •  For
Bushman
(media
violence
ex.),
s
=
4.40
 Step
2:
Set
Cri$cal
Region
 •  Alpha
=
.05
 •  N
=
101
 •  2‐tailed
 Degrees
of
Freedom
 •  Skewness
of
sampling
distribu$on
of
variance
 decreases
as
n
increases
 •  t
will
differ
from
z

less
as
sample
size
 increases
 ...
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This note was uploaded on 04/02/2014 for the course PSY 418 taught by Professor Haley during the Spring '08 term at University of Texas.

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