In a large group of introductory statistics students the pro

In a large group of introductory statistics students, the probabilities of being in the various years at school are 0.10 first year, 0.60 second year, 0.20 third year, and 0.10 fourth year.

____ 1. The possible values for the variable of interest are

independent

non-overlapping

At a particular university, the probability of a student living on campus is 0.50; the probability of a student smoking is 0.20. The probability of living on campus and smoking is 0.05.

____ 2. Do living situation and smoking appear to be independent?

yes, exactly

yes, approximately

no; the probability of smoking seems significantly higher for on-campus students

no; the probability of smoking seems significantly lower for on-campus students

An article entitled, Merck halts testing of AIDS vaccine reported that 24 of 740 volunteers who got the vaccine in one segment of the experiment later became infected with HIV, the virus that causes AIDS. In a comparison group of volunteers who got dummy shots, 21 of 760 participants also became infected.

Vaccine

716

740

Placebo

739

760

Total

1455

1500

____ 3. The risk of HIV was

about the same for vaccine recipients, compared to placebo recipients

a bit lower for vaccine recipients, compared to placebo recipients

much higher for vaccine recipients, compared to placebo recipients

Some women who develop preeclampsia during pregnancy are found to have hypertension causing autoantibodies in their blood for up to two years after delivery. Researchers are interested in the link between preeclampsia and the occurrence of these antibodies.

Autoantibodies

No autoantibodies

Preeclampsia

Normal

Total

____ 4. Apparently, preeclampsia and autoantibodies are

independent

dependent

non-overlapping

The Defense Department\'s mass mental health screening of service members returning from ground combat operations from May of 2003 to April of 2004 looked at where the soldiers had served, and whether the soldiers accessed outpatient mental health services upon their return.

Iraq

77,700

144,300

222,000

Other Location

17,160

60,840

78,000

Total

94,860

205,140

300,000

____ 5. Apparently, location served and accessing mental health services are

independent

dependent

Researchers at Carnegie Mellon University wanted to see if people\'s desire for variety in snacks was more pronounced when two different snacks were offered simultaneously, as opposed to sequentially. They reasoned as follows: \"If you have just eaten an orange it might well make an immediate second orange less appealing, but it will probably have little effect on the pleasure of an orange eaten tomorrow.\" This table shows counts of subjects taking two of the same kind of snack, and those taking one each of two different kinds of snack, when offered a variety of snacks under two conditions: some subjects were offered the snacks sequentially, one a week for two weeks, and others were allowed to take two snacks simultaneously at one time.

____ 6. Under which condition were subjects more likely to choose two of the same snack?

when snacks were offered sequentially

when snacks were offered simultaneously

no real difference

____ 7. Does the table seem to provide evidence of a relationship in general between whether snacks are offered simultaneously or sequentially and whether the someone chooses both the same or two different?

yes

____ 8. Which of these marketing strategies seems to make sense, given the results of the study?

When a large number of snacks are packaged in bulk, vary them to make the package more appealing to consumers.

When a large number of snacks are packaged in bulk, offer all the same type to appeal to consumers who prefer one certain snack.

Researchers carried out a study on small children, where they pretended to go shopping together and then recorded the imaginary purchases. Of interest were whether or not the children \"bought\" (pretended to buy) cigarettes, and whether or not the children\'s parents smoked. Results are shown in the table below.

Bought Cigarettes

Didn\'t Buy Cigarettes

Total

120

____ 9. The most relevant conditional percentages to compare are

A college student gathered data on whether men were more likely to wash their hands in the restroom if they were aware of someone being present to observe them. In some cases he was visibly present in the library restroom and in other cases he concealed himself in a stall.

Washed Hands

Did Not Wash Hands

Total

____ 10. The explanatory variable in this example is shown in the

columns

rows

it could easily be either

Some inmates of state prisons received Therapeutic Community (TC) drug treatment, while others did not. An evaluation of the program considered whether or not prisoners were reincarcerated within 12 months of their release.

Reincarcerated

Not Reincarcerated

Total

108

264

316

351

424

____ 11. Do reincarceration and being in the TC program appear to be related?

yes

This graph shows the distribution of housefly wing lengths (in millimeters).

____ 12. Which of these is your best guess for the probability of being greater than 4.8 millimeters?

0.01

0.03

0.10

0.30

Lengths of newborn babies (in inches) have a mean of 20 and a standard deviation of 2. Once z-scores are found, this sketch of the tails of the normal curve can be used to estimate probabilities.

____ 13. A newborn with a length of 20 inches is

not at all unusual

somewhat unusual

extremely unusual

ACT scores for a population of students have a mean of 21 and a standard deviation of 5. Once z-scores are found, this sketch of the tails of the normal curve can be used to estimate probabilities.

____ 14. The probability of being greater than 27 is between

between 0 and 0.005

between 0.005 and 0.01

between 0.01 and 0.025

between 0.025 and 0.05

greater than 0.05

Math SAT scores for a certain population are approximately normal with a mean of 610 and a standard deviation of 72.

____ 15. Use the sketch of the tails of the z curve to estimate the probability of a score below 437: between

0 and 0.005

0.005 and 0.01

0.01 and 0.025

0.025 and 0.05

0.05 and 1

____ 16. The plots below are for students\' Math SAT scores (normal), credits taken (left-skewed), hours of sleep (also left-skewed), and weights (right-skewed), in scrambled order. Which one is the normal probability plot for students\' weights?