Practice 3 | Answers Posted: Thursday, May 1st
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- Pg 714: 13.15a by hand OR SAS. Also state the null
and alternate hypothesis in terms of the parameters and
the problem, and check the assumptions.
- Pg. 732: 13.35 b-d by hand and by SAS. Is the sample
size large enough? Is this a test of homogeneity or
of independence? Why?
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10 | Due: Wednesday, April 16
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- Page 522: 11.13c, also calculate the SSE, MSE, and a 95%
confidence interval for the slope.
- Page 526: 11.19 using SAS. Also, check that the assumptions for
performing regression are met, conduct a test of the null hypothesis
that beta_1=0, and construct a confidence interval for the slope.
- Page 548: 11.54 (both what r and r2 tell us)
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9 | Due: Monday, April 14
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- Page 459: 10.18 a, b, c
- Page 461: 10.24 a Use SAS to generate your own output and
check the assumptions
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8 | Due: Wednesday, April 2
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- Page 405: 9.32
- Page 365: 8.76
- Sketch two sample power curves (on the same
graph) for testing H0: mu=0 vs.
HA: mu < 0 for alpha=0.10.
Make one of the curves for a large sample size
and the other is for a small sample size. (Be sure and label them!)
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Practice 2 |
Answers posted:
Friday, March 21
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- Pg. 352: 8.57
- Pg. 357: 8.62
- Pg. 370: 8.88
- Pg. 392: 9.10
- Pg. 415: 9.51
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7 | Due: Wednesday, March 19
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- Consider the "Scallops, Sampling, and the Law" box write-up and focus
questions on page 319. The rule of comparing x-bar to a cut-off could
be considered unfair because we don't really want to compare x-bar to the
cut-off... we want to compare mu to the cut-off. In this case, what we
want is for mu to be at least one for the catch to be legal.
- By hand, construct a 95% confidence interval for the mean weight
measurement for a bag of shrimp from this boat. (You may use the
facts that x-bar=0.9317 and s=0.0753).
- Does the catch appear to be legal?
- By hand, construct a 95% confidence interval for the standard deviation
for the weight measurements for a bag of shrimp from this boat. (Again,
you may use the fact that x-bar=0.9317 and s=0.0753).
- Use SAS to construct both a 95% CI for the mean and a 95% CI for
the standard deviation of the weights of the bags. Remember that whenever
you use SAS with your homework you need to include a copy of the code from
the Program Editor window and the appropriate part of the output.
(The CI for the sd may be slightly different in SAS than by hand.)
- Use SAS to construct a Q-Q plot of the observed weights.
Does the data seem like it came from a distribution that was very close to
normal, somewhat close to normal, or not at all normal?
- Based on your answer to e, do you trust the confidence interval you made
for the mean to actually be a 95% confidence interval for the mean? do you
trust the confidence interval you made for the standard deviation to actually
be a 95% confidence interval for the standard deviation?
- Pg. 313: 7.41 (Show your work!)
- Pg. 320: 7.54 (Show your work! This one is a lot easier if you've read
page 318 and 319)
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6 | Due: Wednesday, March 5
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- Pg. 272: 6.8 and also
f) Find the sampling distribution of the sample standand deviation s for
n=2.
g) Show that s is a biased estimator for sigma.
- For n=25 (df=24), find P(t>2.492), P(t<1.318) and P(chi2>33.1963)
- Page 305: 7.24a
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5 | Due: Wednesday, February 27
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Show your work for any credit!
- Pg. 248: 5.57 a, also show that n
is large enough
- Pg. 248: 5.62 also show that n
is large enough
- Pg. 279: 6.18
- Pg. 280: 6.28 a-b, also say why the np, n(1-p)
rule doesn't apply
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Practice |
Answers posted:
Friday, February 14
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- Pg. 186: 4.22 part a only
- Pg. 201: 4.52, also
f) What is the probability that the psychic would get exactly
two correct if they had no ESP?
g) What is the probability that the psychic would get exactly two correct
if they had ESP with p=0.5?
- Page 234: 5.16 a,d; 5.20 d; 5.24 c
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4 | Due: Wednesday, February 12
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- Pg. 128: 3.26 begin by writing out the sample space
- Pg. 167: 3.107 b,c (show your work, beware the book answers!)
- Pg. 169: 3.116
- Pg. 170: 3.124 a
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3 | Due: Wednesday, February 5
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For this assignment use the data set in problem 2.15 on page 29. (The dataset
can be found on the CD that came with the book.)
- Using SAS calculate the mean, median, and standard deviation
of this data set. (Remember to include a copy of the code you ran and
the output.)
- In general, would the mean or median be more useful for getting
an idea of how much oil is spilled in a typical accident? Why?
- Would you classify any of the reported spillage amounts as outliers?
Why or why not? (e.g. What rule did you use?)
- Use SAS to construct a Q-Q plot for this data. Does the data
appear to follow a normal curve for the most part?
- Count the number of measurements in the intervals
mean +/- s, mean +/- 2s, and mean +/- 3s, and convert these
raw counts into percentages.
- Compare the percentages found in 5 to the Empirical Rule
and Chebyshev's rule. Does this seem reasonable in light of
your conclusion in part 4?
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2 | Due: Wednesday, January 29
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- Pg. 59: 2.56b (Show all your work.)
- Consider the data in problem 2.56b on page 59.
a) Find the mean, median, standard deviation and
variance if each number in the data set is multiplied by 2.
b) Find the mean, median, standard deviation and
variance if each number in the data set has 2 added to it.
c) Write down a general rule about the effect on the mean, median,
standard deviation, and variance when the data is multiplied by
a constant.
d) Write down a general rule about the effect on the mean, median,
standard deviation, and variance when the data has a constant
added to it.
- Pg. 68: 2.75, explain how you got your answers!
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1 | Due: Wednesday, January 22
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- Read page 15, and consider the AAUW study at the bottom
concerning the happiness of high school girls.
a) Is the response of each girl to the question qualitative
or quantitative?
b) What is misleading about saying that "only 29% of high school
girls" are happy with themselves? (Hint: What does it imply about the
other 71% and why isn't this true?)
c) The AAUW compared the high school girls to elementary school
girls. Think of another group that they could be compared to and argue
(in a sentence or two) why your choice might be better.
d) Why does it seem unreasonable that this is truly a random
sample as defined on page 12. (Hint: What would you need to have in
order to choose such a random sample).
- Consider the data in 2.21 (pg. 38)
a) If you were to make a histogram
for this data set, why would it be somewhat misleading to combine the first
two classes into a single class from 0.0 to 0.9? (I mean, the others are
all one long, why not this one?)
b) Say the bar for the class 1.0-1.9 was drawn to go from 0.95 to 1.95 and
was 5.8 units high. Similarly the bar for
for the class 2.0-2.9 went from 1.95 to 2.95 and was 30.8 units high.
Describe the bars for the separate classes 0 and 0.1-0.9, and also the bar
that the joined class would have.
- For the data in 2.56b (pg.59) calculate the mean, median, and mode.
Is this data set skewed (if so, in which direction) or symmetric?
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