Math 151 , Fall 2004, Monday Day 41, December 6 Hit
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HW assignment Day 41
Read 7.2.
You are responsible for the concepts
material through p. 402;
should read and understand the rest in order to be able to deal with
the
output from SPSS, and future encounters. Up to p. 402 is the last
material you're responsible for.(The horrible formula
on
p. 403 is the one SPSS uses to find the d.f. You do NOT need to
know
it--I do not expect you to ever calculate it by hand.)
Hand in Wednesday ( SPSS is working
in the labs as of Fri. afternoon. Also in the classroom):
Longer,
more detailed version of the
handout for SPSS on two-sample problems here, +
in white folder outside my door
.
By hand: These are optional this term.
p. 401, 7.34 beetles in oats (test)
p. 412, 7.49 voice onset time (test and CI)
= = = = = = = = = = = = = = = = = = =
=
= = = = = = = = = =
Due Wednesday: More
complicated problems: putting together everything...
Read them over, do what
you can, bring questions ? These are
all 2-sample questions. I expect all of the SPSS work, but I
don't expect lengthy hand computations (7.45,
67, 72) The comments tell you what to do/not do in those
problems. They are worth looking at for the style of presentation
of data, what are the hypotheses, CI's of what, etc. even if you don't
do all the computation requested in the problem..
(SPSS) p. 400, 7.33 Math sublimina. This
is a complicated design: matched pairs, then 2-sample on the
differences!
But notice chicks (7.35 ) was also matchedpairs--weight gain
=after-before--but
they gave us the pre-subtracted numbers.
p.410, 7.45 fitness Do b. Then
Look in the back at the answers for a and b. (Don't bother to do
the computations yourself)
(SPSS) p.422, 7.63 pasture fertilization
p.423 7.67 London bus people, rest.
You did
a, d day 39. See which numbers are relevant for each part.
Read the answers.
p.425 7.72 reading biology Do a,b,c, and for d, find xbars
and s's. Don't finish the tests.
|
Final
exam:
Tuesday, Dec. 14, 2-5 p.m. See me if you have a conflict.
The Final will be closed book, but bring one sheet with your
notes.
Length 1 1/2 to2 times the length of the midterm exams; comprehensive
but
with special attention to the material covered since Exam 3.
Reading
but not creating SPSS.
Get handout
of info and review problems, if you didn't last time.
~~~~~~~~~~~~~~~
Sec.
7.2,
Comparing two means Homework questions, SPSS?
See Day
39 Summary:
"Two-sample tests". Two SRS's, independent, from
distinct
populations. (Populations are normally distributed)
To examine the difference of the two means, µ1
- µ2:
Use diff = xbar1 - xbar2
= 
.
Same thing:
Not quite t, but close:
For doing by hand:
df = smaller of (n1- 1) and (n2- 1).
Will
give a "conservative" result--slightly wider C.I., slightly less
significance.
From a computer: df
= complicated formula on p. 403. Produces non-integer
degrees
of freedom. Use if both sample sizes are at least 5. Unsuitable
for doing by hand.
CI : estimate + t* . SEestimate
CI for µ1 - µ2,
difference of
means, is 
Test: H0: µ1 - µ2
= 0 same as µ1 = µ2 , "no
difference"
always
Ha: µ1
- µ2 > 0 same as µ1
> µ2
or Ha: µ1
- µ2 < 0 same as µ1 <
µ2
or Ha: µ1
- µ2
0 same as µ1
µ2 (not equal)
Calculate t, find P-value
(approximate, conservative, Better from SPSS)
--SPSS will do our computations when we
are given raw data.
Handout for SPSS two-sample, section 7.2
Last side of "Statistical inference" handout. Longer
version of 2-samp
(p.3 is optional: tables built in to SPSS).
Go through text example, other HW examples.
Analyze>Compare means>
Independent-samples
t.
We use the Not-equal-variances line of
the results.
Will be optional: Example
of
hand computation
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