| from Moore
Sketching xbars for H0, p-value p. 323, 6.25 SSHA 6.26 Spending on housing - - - - - - - - - - - - - - - - - - - Stating null and alternative hypotheses p. 325 6.27, 28, 29, 30 - - - - - - - - - - - - - - - - - - - Calculating p-value (one-sided), relating to Sig. level p. 328, 6.31 and 32 (extending 6.25 and 26) 6.33 restating jargon - - - - - - - - - - - - - - - - - - - Calculating p-value (one or two-sided), using z test statistic, relating to Sig. level p. 333, 6.34 price reduc. on coffee 6.35 crankshafts true? Use your calculator to find the sample mean. 6.36 cola? Use your calculator to find the sample mean. |
Read,
to discuss |
Optional
(more practice) Stating null and alternative hypotheses
|
Add your shoebox results to each of
the 2 sheets
circulating:
the 4 values || xbar|| z (assuming mean is 20)||
P-value=P(Z > z)|| Is P-value < .10?
Add a dot for each of your xbars to the dotplot transparency
circulating.
CI
quiz returned: 10 pts possible.
Needed to memorize.
If you got less than 8 pts, you may retake
the quiz, for a max of 8 points, Friday before or after class, or by arrangement.
HW question: 6.2 ?
Significance testing
Introduction Day31
Shoebox results:
We got a higher proportion than anticipated from the white shoebox in the
P>.10 region. (Should have gotten about 10%) Misfiled
numbers?
2-sided (2-tailed) test:
H0: "Null hypothesis" A
claim or statement about the population we would like to show is
NOT true.
H0:
µ =1000 hrs. (Average lightbulb life.)
Ha: "Alternative hypothesis"
A claim or statement about the population we are trying to find
evidence FOR. A value either much bigger than or much smaller
than the H0 value is evidence against H0 & for
Ha.
Ha: µ Not = 1000 hrs. (Quality control
on assembly line--find if it is "off" either way.)
Sample of size n = 25.
Population sigma = 150 hrs. Suppose xbar = 940 hrs. z
= (940-1000)
÷
(150/5) = -2
P-value: We measure the probability
of seeing something (again) as extreme as the observed value
(or more so).
So you need to measure the P-value symmetrically
both directions from the observed value--so the P value is double
what it would be for a one-sided test. P-value
is approximately 5%; more precisely, 2·.0228 = .0456
Our test is just
barely significant at the .05 level; it is
significant at the .06 level, the .10 level. It's not significant
at the .02 level or "higher".
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