University of Minnesota, Twin Cities School of Statistics Stat 3011 Rweb Textbook (Wild and Seber)
You can look at last year's homework assignments to get an idea what future assignments will be like. This year's will be more or less the same. We may cover a little less material than last year. And of course last year's dates don't match this year.
Go to assignment: 1 2 3 4 5 6 7 8 9 10 11
Note: The problems assigned will all be "Exercises" or "Review Exercises" not "Quiz" questions.
No. | Due Date | Ch. or Sec. | Exercises | Comments |
---|---|---|---|---|
1 | Fri Sep 14 | 1.1 | 2, 4 | |
1.2 | 1 | |||
1.3 | 2 | |||
1 (Review) | 2, 3, 6 12, 16 | |||
2 | Fri Sep 21 | 2.3.1 | 1 | |
2.3.2 | 4 | |||
2.3.3 | 2 | histogram only, use computer and use right=FALSE
for comparison with Figure 2.3.8 in the textbook and the
histogram example from class.
| ||
2.3.4 | 2 | |||
2.4.1 | 4 | use computer to find median | ||
2.4.2 | 1(b), 4 | see data entry example from class. | ||
2.4.3 | 2 | |||
2 (Review) | 4, 6 | |||
3 | Fri Sep 28 | 2 (Review) | 9abde | |
3.1.2 | 1, 3 | |||
3 (Review) | 3 | You don't have to do anything special to avoid plotting the 24th point.
Its y value is NA (no value) so it will be ignored.
| ||
4.3 | 1, 3 | |||
4.4.2 | 3 | |||
4.4.3 | 2 | |||
4.4.4 | 2 | |||
4.5 | 1, 4 | |||
4 (Review) | 2, 3 | |||
4 | Fri Oct 5 | 4.7.1 | 2 | |
4.7.3 | 1 | |||
4 (Review) | 5, 18 | |||
5.2 | 1, 5b-i | |||
5.4.1 | 1 | |||
5.4.2 | 2 | |||
5.4.3 | a-i | no number on question, do all parts | ||
5 (Review) | 11 | |||
A | 1, 2 | "additional problems" see below. | ||
5 | Fri Oct 12 | 6.2.2 | 2, 3 | You should also do 1 in the sense of visiting the examples page but needn't hand anything in. |
6.2.3 | 2, 3 | You should also do 1 in the sense of visiting the examples page but needn't hand anything in. | ||
6.2.4 | 1, 2 | |||
6.4.3 | 1abcf, 2 | |||
6 (Review) | 1, 2, 4, 10 | |||
6 | Fri Oct 26 | 7.2.1 | 1 | Note: The answers in the back of the book are correct. The previous comment that they were wrong was itself wrong. |
7.2.2 | 1, 2 | |||
7.2.3 | 1, 3 | Recall that the R command fred <- c(0.513, 0.524, 0.529)
creates a data vector of those three numbers, and similarly for longer
data vectors.
| ||
7.3.1 | 1, 3 | |||
7.5 | 1, 3 | |||
7 (Review) | 4, 10, 12, 20 | |||
7 | Fri Nov 2 | A | 3, 4, 5, 6 | "additional problems" see below. |
7 (Review) | 15 | |||
8.2 | 2 | Recall that the R command fred <- c(0.513, 0.524, 0.529)
creates a data vector of those three numbers, and similarly for longer
data vectors.
| ||
8.3 | 1, 2 | Do each of these problems twice, once using the
methods described in Wild and Seber getting the answer in the back of the
book, then again using the R function prop.test described
in the Lecture Examples for Chapter 8.
| ||
8 (Review) | 1 | |||
8 | Fri Nov 9 | 7.5 | 2 | This problem and the next are paired. The two samples can be obtained
in Rweb by the statements
x <- density[1:6] y <- density[7:29]when you are on the Rweb for 3011 page with the dataset Table 7.2.1 (p. 291) cavend.txtselected in the "Datasets from Wild and Seber" chooser. |
8.4 | 1 | For (a) use the R function t.test , which does the Right
Thing, not the answer in the back of the book.
| ||
8.5 | 1, 2 | |||
8.6 | 1, 2 | |||
8 (Review) | 4, 12 | |||
A | 7, 8, 9 | "additional problems" see below (problem 9 was added Monday). | ||
9 | Mon Nov 26 | 9.2 | 1, 3, 4 | |
9.3 | 2, 3, 7 | |||
9 (Review) | 2, 12, 18 | |||
10 | Wed Dec 5 | 10.1.2 | 1 | |
10.3 | 1, 2, 3, 4, 5 | |||
10 (Review) | 4, 6abdef, 12abcefg | omit part (c) of 6 and part (d) of 12 | ||
11 | Fri Dec 14 | 11.1 | 1 | |
11.2.1 to 11.2.3 | 2 | |||
11 (Review) | 2, 5, 6 | |||
A | 10 | "additional problems" see below. Also see Chi-Square Tests for 2 by 2 Tables for help with additional problem 10 | ||
1. Suppose the probability of a widget being defective is 0.02. Suppose widgets come in boxes of 12. Assume widget defects are statistically independent.
2. For the probability model for the random variable X defined by the following table
x | 0 | 1 |
pr(x) | 1 - p | p |
3. Suppose the random variable T has Student(10) distribution (Student's t-distribution with 10 degrees of freedom).
4. Suppose the random variable T has Student(7) distribution
5. Widgets produced at Acme Widget Works are specified to have 7.00 mm frammis diameter. A random sample of 5 widgets are taken from the production line and their diameters accurately measured. The sample mean was 6.9123 mm and the sample standard deviation 0.0884 mm. Assume that the distribution of frammis diameters is normal, and give an interval that has 95% coverage probability for the true mean frammis diameter of widgets being produced based on Student's t-distribution. Answer: (6.80, 7.02).
6. Jones and Smith are running for Mayor of the town of Outer Boondock. Two polls taken one month apart by the local paper, both with sample sizes of 500, had the results shown below
candidate | first poll | second poll |
---|---|---|
Jones | 37.2% | 42.6% |
Smith | 45.4% | 42.8% |
Undecided | 17.4% | 14.6% |
It appears from the polls that Jones is gaining. But appearances may be deceiving.
7.
Redo part (a) of Additional Problem 6 using the R
function prop.test
rather than hand calculation.
8. Using the data for the first poll in Additional Problem 6 calculate an approximate confidence interval for the difference of proportions of voters favoring Jones and favoring Smith. (Hint: Which of Wild and Seber's three cases is this?)
9. In two polls taken a month apart, each poll sampling 600 likely voters, the preferences expressed for the candidates were
First Poll | Second Poll | |
Shrub | 45% | 50% |
Pierce | 35% | 36% |
Bottom | 12% | 8% |
Undecided | 8% | 6% |
In the second poll the following results were reported for suburban college educated women (67 were in the sample, about 1 / 9 of the sample).
Second Poll | |
Shrub | 62% |
Pierce | 24% |
Bottom | 9% |
Undecided | 5% |
Answer each of the questions below two ways.
quick and dirtyor
mental adjustmentcalculation described in Section 8.5.3 in Wild and Seber or on our web page on the same material.
10. For the two polls in additional question 9 the table below gives the actual counts (how many actual people correspond to each cell of the table), which you need for this problem.
First Poll | Second Poll | |
Shrub | 270 | 302 |
Pierce | 210 | 215 |
Bottom | 72 | 48 |
Undecided | 48 | 35 |
The sample size for both polls was 600.
Obtain a P-value and interpret the P-value, saying what it implies about support for the various candidates.