Some variables that were recorded while studying diets of sharks are given below

| August 30, 2017

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1. Some variables that were recorded while studying diets of sharks are given below. Which of the variables is categorical?

The length of the shark being observed

The type of shark being observed

The amount of food eaten in a day by the shark being observed

The age of the shark being observed

2. During winter, red foxes hunt small rodents by jumping into thick snow cover. Researchers report that a hunting trip lasts on average 19 minutes and involves on average 7 jumps. They also report that, surprisingly, 79% of all successful jumps are made in the northeast direction. Three variables are mentioned in this report. The first variable mentioned is

quantitative and discrete.

ordinal.

quantitative and continuous.

categorical.

3. Here is a stemplot of body temperature (in degrees Fahrenheit) for 65 healthy adult women.

The number of women in the sample that have a body temperature lower than 98 degrees Fahrenheit is

15.

45.

20.

50.

4. Here is a histogram of the yearly number of unprovoked attacks by alligators on people in Florida over a 33-year period.

What is the overall shape of the distribution?

Roughly symmetric with an outlier

Slightly skewed to the right

Bimodal

Strongly skewed to the left

5. A sample of 20 endangered species was obtained and the length of time (in months) since being placed on the list was recorded for each species. A stemplot of these data follows. In the stemplot, 5|2 represents 52 months.

The first quartile of the length of time (in months) since being placed on the list for these 20 species is

74.

59.5.

75.5

5.

6. Here is a dotplot of migraine intensity (on a scale of 1 to 10) for 29 adults suffering from recurring migraines.

The third quartile for this data set is

9.25.

10.

9.5.

9.

7. A maze experiment uses 24 lab rats of various ages, as summarized below.
Age (in months) Number of rats
2 4
3 6
4 6
5 4
7 3
9 1

What is the median rat age (in months) for this maze experiment?

4

5

4.5

3.5

8. Geckos are lizards with specialized toe pads that enable them to easily climb all sorts of surfaces. A research team examined the adhesive properties of 7 Tokay geckos. Below are their toe-pad areas (in square centimeters, cm2).
5.6 4.9 6.0 5.1 5.5 5.1 7.5
Rounded to two decimal places, the mean toe pad area in this sample of geckos is _______ cm2.

9. By inspection, determine which of the following sets of numbers has the smallest standard deviation.

7, 8, 9, 10

5, 5, 5, 5

0, 0, 10, 10

0, 1, 2, 3

10. A researcher states that the survival time of an organism is negatively related to the amount of a specific pollutant present in the ecosystem. This means that

above-average amounts of pollutant tend to accompany below-average survival times.

below-average amounts of pollutant tend to accompany below-average survival times.

below-average amounts of pollutant can be accompanied by either above- or below-average survival times.

above-average amounts of pollutant tend to accompany above-average survival times.

11. Here is the protease activity found in walnuts preserved in buffers of varying pHs:
pH 4.5 5 6 7 8 9 10
protease activity 0.17 0.245 0.28 0.055 0.02 0 0.025

Which of the following scatterplots is a correct representation of the data?

12. Below is a scatterplot of heights (in centimeters) of Spartina alterniflora plants against the amount of sunlight they were given (in minutes). Those plants grown at sea level are represented by a closed circle and those grown on the ISS are shown with an open circle.

We conclude that

there is a weak association for both locations.

association can’t be assessed here since a categorical variable is involved.

there is a strong positive association for sea level plants, but a negative association for ISS plants.

there is a strong association for sea level plants, but a positive association for ISS plants.

13. Tail-feather length in birds is sometimes a sexually dimorphic trait. That is, the trait differs substantially for males and for females. Researchers studied the relationship between weight (x) and tail-feather length (y) in a sample of five wild male long-tailed finches. Here are the data:

The value of the linear correlation coefficient between weight and tail feather length is approximately

0.942.

0.888.

0.789.

We should not be computing this value because the relationship is not linear.

14. Tail-feather length in birds is sometimes a sexually dimorphic trait. That is, the trait differs substantially for males and for females. Researchers studied the relationship between tail-feather length (measuring the R1 central tail feather) and weight in a sample of 20 male and 21 female long-tailed finches raised in an aviary.

Which of the following statements is NOT true?

Overall, females tend to have smaller tail feathers than males, for a given body weight.

Both males and females show a clear positive linear relationship between weight and tail-feather length.

Male birds that are heavier tend to have longer tail feathers.

There appears to be no relationship between body weight and tail-feather length in female birds.

15. Suppose we fit the least-squares regression line to a set of data. Points with unusually large values of the residuals are called

outliers.

response variables.

correlated.

the slope.

16. John’s parents recorded his height at various ages up to 66 months. Below is a record of the results.

John’s parents decide to use the least-squares regression line of John’s height on age based on the data in the previous problem to predict his height at age 21 years. We conclude that

John’s height, in inches, should be about half his age, in months.

the parents will get a fairly accurate estimate of his height at age 21 years because the data are clearly correlated.

such a prediction could be misleading because it involves extrapolation.

All of the above

17. A researcher noticed that, for streams along the east coast, the amount of money spent on restoration and the number of distinct fish populations present appeared to have a negative correlation.

To investigate this, the researcher should begin his research by using

the least-squares regression line.

a well-designed experiment.

the correlation coefficient.

the square of the correlation coefficient.

18. Tail-feather length in birds is sometimes a sexually dimorphic trait. That is, the trait differs substantially for males and for females. Researchers studied the relationship between weight (x) and tail-feather length (y) in a sample of five wild, male long-tailed finches. Here are the data:

The value of the y intercept for the least-squares regression line is

25.547 mm.

25.547 mm/g.

2.815 mm/g.

2.815 g/mm.

19. At a local health club, a researcher samples 75 people whose primary exercise is cardiovascular and 75 people whose primary exercise is strength training. The researcher’s objective is to assess the effect of type of exercise on cholesterol. Each subject reported to a clinic to have his or her cholesterol measured. The subjects were unaware of the purpose of the study, and the technician measuring the cholesterol was not aware of the subject’s type of exercise. This is a(n)

double-blind experiment.

observational study.

experiment, but not a double-blind experiment.

matched pairs experiment.

20. The city council in a suburb of Raleigh is interested in the level of public support for a tax increase to support restoration of nearby parks and waterways. A marketing research firm is selected that then selects a simple random sample of 50 adult residents and contacts each to determine whether the resident would be opposed to the tax increase. Of these, 15 indicated that they would be opposed.

The sample is

the 50 residents selected.

the 15 residents not in favor of the increase.

all residents in the suburb.

the 35 residents in favor of the increase.

21. A student organization at a local college posted a poll on its website. After a semester, the results were tallied and it was found that 95% of the respondents were in favor of raising fees to increase funding for student organizations. This conclusion was based on data collected from 5000 votes cast on the website. Based on the IP addresses of the respondents, it was later determined that 3200 of the votes were cast from a single off-campus computer belonging to a member of the student organization that posted the poll. The results of this poll are probably

biased, but only slightly since the sample size was quite large.

reliable since there were still 1800 other randomly obtained respondents.

biased, overstating the popularity of raising fees.

biased, understating the popularity of raising fees.

22. An SRS of 1200 adult Americans is selected, and each person is asked the following question.

“In light of the huge national deficit, should the government at this time spend additional money to establish a national system of health insurance?

Only 39% of those responding answered “yes.” This survey

probably overstates the percent of people that favor a system of national health insurance.

is very inaccurate, but neither understates nor overstates the percent of people that favor a system of national health insurance. Since simple random sampling was used, it is unbiased.

is reasonably accurate since it used a large, simple random sample.

probably understates the percent of people that favor a system of national health insurance.

23. You need to select three subjects from a list of nine subjects. The subjects’ names are provided below.
1. Berliner 4. Wolfe 7. Verducci
2. Blumenthal 5. Stasny 8. Lin
3. MacEachern 6. Santner 9. Critchlow

Use the numerical labels attached to the names and the following list of random digits to select three individuals. Read the list of random digits from left to right, starting at the beginning of the list.
44982 20751 27498 12009 45287 71753 98236 66419 84533 11793 20495 05907 11384

Which of the following statements is TRUE?

If we used another list of random digits to select the sample, we would get a completely different sample than that obtained with the list actually used.

If we used another list of random digits to select the sample, the result obtained with the list actually used would be just as likely to be selected as any other set of three names.

If we used another list of random digits to select the sample, we would get the same result as obtained with the list actually used.

If we used another list of random digits to select the sample, we would get at most one name in common with a name obtained with the list actually used.

24. An experiment has a double-blind design when neither the investigators nor the subjects

know or meet each other before the study is over.

know that an experiment is going on.

know which subjects have been assigned to which treatments in a list of known treatment options.

know the purpose of experiment.

25. The drug valproate has been shown in mice to facilitate adult learning of skills typically acquired during early life. A study enrolled healthy adult males with no advanced musical training and taught them to identify absolute pitch, a rare ability typically learned in early childhood. In a first stage, the participants were randomly assigned to valproate or a placebo. In a second stage, the conditions were reversed, so that a participant who received the placebo first took valproate for the second stage, and vice versa. This is an example of a(n)

experiment with a block design.

case-control observational study.

matched pairs or repeated measures experiment.

completely randomized experiment.

26. The Physicians’ Health Study followed 22,000 male physicians for a period of several years. About 11,000 took an aspirin every second day, while the rest took a placebo. At the completion of the study, it was noted whether a subject had experienced a heart attack during the period of the study. It was found that the aspirin group had significantly fewer heart attacks than the placebo group.

The factor in the experiment is the

medication used (aspirin or placebo).

use of a placebo.

severity of the heart attack.

length of the study.

27. A study attempts to determine whether a new medication is effective at lowering blood pressure. Forty subjects with hypertension who volunteer to participate in the study are to be given both the new medication and a placebo. The order in which each subject receives the treatment is randomized and the subject does not know which treatment they are getting. Each treatment is administered for four weeks. At the end of each four-week period a subject’s blood pressure is recorded.

This is an example of

the placebo effect.

a double-blind observational study.

a stratified analysis.

a matched pairs experiment.

28. Consumer Reports compared the effectiveness of an anti-wrinkle cream with that of a plain moisturizer in reducing the appearance of wrinkles. They enrolled 79 subjects with moderate to marked wrinkles, and instructed them to use both products, one on each side of the face, every morning for 12. The subjects didn’t know which products they were using. At the end of the study, panelists examined “before and after” photos of the subjects to assess wrinkle appearance. The panelists did not know which product the subjects had used. Which of the following statements is TRUE?

This study was a randomized, double-blind experiment.

This study was a double-blind experiment, but not a randomized experiment.

This study was an experiment, but not a double-blind experiment.

This study is just anecdotal.

29. A researcher is trying to determine the proportion of a certain species of fish in a local lake. After sampling 40 fish, she found 32 of them were the species of interest. She estimates the probability that the next fish is of the species of interest to be

0.50.

1.25.

0.32.

0.80.

30. Event A has probability 0.4. Event B has probability 0.5. If A and B are disjoint, then the probability that both events occur is

0.1.

0.9.

0.2.

0.0.

31. A variable whose value is a numerical outcome of a random phenomenon is called

a random variable.

biased.

a parameter.

a random sample.

32. A physician observes the number of lesions on subjects who had regularly used tanning salons. Let X be the number of lesions observed. The physician found that X had the following probability distribution.
Value of X 0 1 2 3 4
Probability 0.05 0.1 0.25 0.30 0.30

P(X > 3) has value

0.7.

0.4.

0.6.

0.3.

33. Based on data from the USDA, we define the following probability model for the number X of different pesticides detected in fresh produce.
X 0 1 2 3 4 5 or more
Probability 0.43 0.17 0.14 0.08 0.06 0.12

The numerical value for the probability P(X –2.62 is

0.0044.

0.0047.

0.9956.

0.9953.

35. The pH measurements of water specimens from various locations along a given river basin are Normally distributed with mean 8 and standard deviation 0.3.

What is, approximately, the probability that the pH measurement of a randomly selected water specimen is greater than 8.2?

0.2475

0.7525

0.2525

0.7475

36. The pH measurements of water specimens from various locations along a given river basin are Normally distributed with mean 8 and standard deviation 0.3.

Three-quarters of the pH measurements in this river basin are greater than

8.402.

8.202.

7.798.

8.450.

37. A researcher is interested in the lengths of Salvelinus fontinalis (brook trout), which are known to be approximately Normally distributed with mean 80 centimeters and standard deviation 5 centimeters. To help preserve brook trout populations, some regulatory standards need to be set limiting the size of fish that can be caught. The probability of catching a brook trout less than 72 centimeters in length is

0.9452

0.6255.

0.0548.

0.3745.

38. The distribution of total body protein in adult men with liver cirrhosis is approximately Normal with mean 9.8 kg and standard deviation 0.1 kg.

Twenty-five percent of adult men with cirrhosis have a total body protein of at least

9.87 kg.

9.70 kg.

9.73 kg.

9.60 kg.

39. The amount of cholesterol in a person’s body produced by their liver and other cells is proposed to be Normally distributed with mean 75% and standard deviation 0.5%.

The probability that a person produces more than 76.7% of the cholesterol in their body is

0.0006.

0.9997.

0.0003.

1.

40. Sale of eggs that are contaminated with salmonella can cause food poisoning among consumers. A large egg producer takes an SRS of 200 eggs from all the eggs shipped in one day. The laboratory reports that 11 of these eggs had salmonella contamination. Unknown to the producer, 0.2% (two-tenths of one percent) of all eggs shipped had salmonella. In this situation,

0.2% is a parameter and 11 is a statistic.

11 is a parameter and 0.2% is a statistic.

both 0.2% and 11 are parameters.

both 0.2% and 11 are statistics.

41. You plan to randomly select 10 students from your campus and ask them how many minutes they exercised in the past seven days.

The distribution of values taken by the average exercising time in all possible samples of size 10 is the

sampling distribution of average exercising times.

probability distribution of exercising times.

population parameter.

variance of the exercising time values.

42. The variability of a statistic is described by the

spread of its sampling distribution.

stability of the population it describes.

vagueness in the wording of the question used to collect the sample data.

amount of bias present.

43. The average age of trees in a large local park is 60 years with a standard deviation of 2.2 years. A simple random sample of 400 trees is selected, and the sample mean age of these trees is computed.

The probability that the average age of the 400 trees is more than 60.1 years is

0.4801.

0.8186.

0.1814.

0.0001.

44. The distribution of total body protein in healthy adult men is approximately Normal with mean 12.3 kg and standard deviation 0.1 kg.

If you take a random sample of 16 healthy adult men, what is the probability that their average total body protein is between 12.25 and 12.35 kg?

0.9876

0.0227

0.9545

0.0455

45. Here is a histogram of T-cell velocities in vitro (in micrometers per minute):

Which of the following statements is NOT true?

The population distribution of T-cell velocities is most likely skewed to the right.

The sampling distribution of T-cell velocities for samples of size n = 10 is very likely right-skewed.

The sampling distribution of T-cell velocities for samples of size n = 100 is approximately Normal.

A histogram of T-cell velocities would be more Normal if the researchers had collected more data.

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