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Stat 3011 (Geyer) Final Exam (Computer Lab Part)

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General Instructions (Please Read!)

• For simple computer commands, you may write the command you used and the result it gave on this test form.
• For complicated commands or plots, make a printout and attach the printout to the test form (we'll provide a stapler).

Question 1 [25 pts.]

Suppose heights of American adult women are normally distributed with mean 63.5 inches and standard deviation 2.5 inches.

1. Find the probability that a women randomly chosen from this population is taller than 67 inches.
2. Find the probability that a women randomly chosen from this population is between 60 and 65 inches tall.
3. Find the 80th percentile of this height distribution.

You may use the form below to answer this question.

If you want to print your results (not necessary, you can write the R commands you used on the test paper instead), replace "your name here" with your actual name in quotes.

Question 2 [20 pts.]

The file munch.dat contains two variables named open and closed consisting of measurements of loudness in decibels of noise made by chewing potato chips with mouth open and mouth closed (a study like this was actually done, the data here are simulated to have the same means and standard deviations). There were 10 subjects in each group (different subjects in the two groups, so 20 subjects in all). We want to do a test of significance of whether there is a difference between the two groups.

1. Should we do a one-tailed or a two-tailed test? Explain. If you chose one-tailed, make clear which tail.
2. Write out the null and alternative hypotheses that go with the procedure you chose in part (a).
3. Do the test, computing the P-value.
4. Interpret the P-value in terms of munching potato chips. What is the conclusion?

You may use the form below to answer this question.

The form automatically loads this data set munch.dat (like the lecture section examples). You don't need to do anything to load the data.

If you want to print your results (not necessary, you can write the R commands you used on the test paper instead), replace "your name here" with your actual name in quotes.

Question 3 [25 pts.]

Before a 1977 supreme court decision, doctors, lawyers, and other professionals were forbidden to advertise in most states. A study about acceptability of advertising by dentists was done soon after. It asked both consumers and dentists to respond to the statement "I favor the use of advertising by dentists to attract new patients." The possible responses were the column labels in the table below.

We want to do a test about whether any difference in attitudes of dentists and consumers is revealed by this study.

1. Describe the test that should be done to address this question.
2. Describe the null and alternative hypotheses that go with the procedure you chose in part (a).
3. Do the test, computing the P-value.
4. Interpret the P-value in terms of attitudes of dentists and consumers. What is the conclusion?

You may use the form below to answer this question. The commands already typed into the form create the table above as a matrix data and print the table so you can see it. All you need to do is add the commands for the statistical analysis.

If you want to print your results (not necessary, you can write the R commands you used on the test paper instead), replace "your name here" with your actual name in quotes.

Question 4 [25 pts.]

The file scores.dat contains two variables named SAT and GPA consisting of math SAT scores and first-year GPAs for 100 students.

1. Make a scatter plot of the data, plotting SAT on the x-axis. Add the regression line of GPA on SAT.
2. Is there a statistically significant linear relationship between these two variables? Explain.
3. Give a 95% prediction interval for the first-year GPA of an individual randomly chosen from the same population having a math SAT score of 650.

You may use the form below to answer this question.

The form automatically loads this data set scores.dat (like the lecture section examples). You don't need to do anything to load the data.

Put your name on the plot before printing it. Either replace "your name here" with your actual name in quotes, or add the optional argument main="your name" to the plot command.