Stream quality is based on the levels of many variables

1. 

Stream quality is based on the levels of many variables, including the following. Which of these variables is quantitative?

2. 

Which of the following is a discrete variable?

3. 

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

4. 

A sample of 55 streams in severe distress was obtained during 2007. The following is a bar graph of the number of streams that are from the Northeast, Northwest, Southeast, or Southwest. In the bar graph, the bar for the Northeast has been omitted. The number of streams from the Northeast is

5. 

Here is a stemplot (with split stems) of body temperatures (in degrees Fahrenheit) for 65 healthy adult women. The first quartile for this data set is

6. 

Researchers measured the length of the central retrix (R1), a flight-involved tail feather, in 21 female long-tailed finches. Here is a boxplot of the length, in millimeters (mm).

Based on this boxplot, which of the following statements is TRUE?

7. 

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).

To be an outlier, an observation must fall outside the range

8. 

The median age of five people on a committee is 30 years. One of the members, whose age is 50 years, resigns. The median age of the remaining four people in the committee is

9. 

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

10. 

The volume of oxygen consumed (in liters per minute) while a person is at rest and while he or she is exercising (running on a treadmill) was measured for each of 50 subjects. The goal is to determine if the volume of oxygen consumed during aerobic exercise can be estimated from the amount consumed at rest. The results are plotted below. The scatterplot suggests that

11. 

Bird species from temperate regions must cope with relatively short breeding seasons. A study examined the relationship between blood testosterone level (ng/ml) and the duration of the egg-laying period (months) in temperate bird species. The scatterplot below displays this relationship, after taking the logarithm of each variable.

A plausible value for the correlation between the logarithm of egg-laying duration and the logarithm of testosterone level is

12. 

When water flows across farm land, some of the soil is washed away, resulting in erosion. An experiment was conducted to investigate the effect of the rate of water flow (in liters per second) on the amount of soil washed away (in kilograms). The data are given in the following table.

The association between flow rate and amount of eroded soil is

13. 

Which of the following is TRUE of the correlation coefficient r?

14. 

Researchers want to know if reading skills can explain IQ test scores in children with dyslexia. The following scatterplot examines the relationship between reading skill score and IQ test score for 22 dyslexic children. The least-squares regression line is displayed on the plot, along with the value of r2.

The intercept of the least-squares regression line

15. 

Researchers want to know if reading skills can explain IQ test scores in children with dyslexia. The following scatterplot examines the relationship between reading skill score and IQ test score for 22 dyslexic children. The least-squares regression line is displayed on the plot, along with the value of r2.

What percent of the variation in IQ test scores is explained by this regression model?

16. 

Before surgical removal of a diseased parathyroid gland, two tests are often performed: the standard intact test and the turbo test. Both tests measure parathyroid hormone (PTH, in ng/l), but the turbo test is very expensive. Researchers obtained data from both tests in a sample of 48 patients to predict turbo test results (y) from standard intact test results (x). The data ranged from roughly 0 to 500 ng/l, and a scatterplot showed a clear linear relationship. The published findings are summarized exactly as follows:

y = 1.08x – 4.36 (r = 0.97; n = 48)

For a PTH level of x = 1000 ng/l with the standard intact test, the predicted PTH level with the turbo test

17. 

Babies typically learn to crawl approximately six months after birth. However, it may take longer for babies to learn to crawl in the winter, when they are often bundled in clothes that restrict their movement. Thus, there may be an association between a baby's crawling age and the average temperature during the month they first try to crawl. Below are the average ages (in weeks) at which babies began to crawl for a sample of babies born in each of the 12 months of the year. In addition, the average temperature (in °F) for the month that is six months after the birth month is also listed.

We want to investigate if the average age at which infants begin to crawl (y) can be predicted from the average outdoor temperature (x) six months after birth, when they are likely to begin crawling. We decide to fit a least-squares regression line to the data with x as the explanatory variable and y as the response variable. We compute the following quantities. r = correlation between x and y = –0.7 = mean of the values of x = 50.25 = mean of the values of y = 31.77 sx = standard deviation of the values of x = 15.85 sy = standard deviation of the values of y = 1.76 Which of the following is closest to the slope of the least-squares line?

18. 

Babies typically learn to crawl approximately six months after birth. However, it may take longer for babies to learn to crawl in the winter, when they are often bundled in clothes that restrict their movement. Thus, there may be an association between a baby's crawling age and the average temperature during the month they first try to crawl. Below are the average ages (in weeks) at which babies began to crawl for a sample of babies born in each of the 12 months of the year. In addition, the average temperature (in °F) for the month that is six months after the birth month is also listed.

We want to investigate if the average age at which infants begin to crawl (y) can be predicted from the average outdoor temperature (x) six months after birth, when they are likely to begin crawling. We decide to fit a least-squares regression line to the data with x as the explanatory variable and y as the response variable. We compute the following quantities. r = correlation between x and y = –0.7 = mean of the values of x = 50.25 = mean of the values of y = 31.77 sx = standard deviation of the values of x = 15.85 sy = standard deviation of the values of y = 1.76 The fraction of the variation in the values of a response y that is explained by the least-squares regression of y on x is the

19. 

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 population of interest is

20. 

The National Health and Nutrition Examination Survey (NHANES) assesses the health and nutritional status of Americans. A recent NHANES asked a random sample of 17,567 American adults to fill a detailed questionnaire about what they ate the previous day and give their body mass index (BMI). The researchers then compared individuals who ate avocado with those who didn't, and found that BMI was lower, on average, among those who ate avocado. This is an example of

21. 

You need to select three subjects from a list of nine subjects. The subjects' names are provided below.

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?

22. 

Sixty-four pregnant women ranked the severity of their heartburn during pregnancy. Researchers rated newborn hair volume using photographs of the newborn's head. They found an association between heartburn severity during pregnancy and the amount of hair on newborns. What can we reasonably conclude from this study?

23. 

A March 2010 SurveyUSA telephone poll asked about issues facing central Ohio to a random sample of 500 households in the Columbus, Ohio, area. One question was: “Where 10 means most important, and 1 means least important, how important is protecting the environment?” The average response was 6.0. What population is the poll targeting?

24. 

A researcher is interested in investigating the relationship between sugar consumption and weight gain for high school students. Fifteen volunteers were randomly assigned to one of two groups. The first group contained six volunteers who were put on a low-sugar diet. The second group consisting of the remaining nine volunteers was put on a diet with sugar constituting approximately 15% of their diet. After eight weeks, the change in weight was recorded for each of the volunteers. The response is the

25. 

A researcher was studying how the weights of horseshoe crabs along the east coast varied between northern and southern habitats. In spring 2006, during breeding season, the researcher randomly selected 50 horseshoe crabs in southern habitats. In fall 2006, before breeding season begins, the researcher randomly selected 50 horseshoe crabs from northern habitats. It was found that crabs in southern habitats weighed more and so the researcher claimed that location had an effect on weight of horseshoe crabs. The results cannot be trusted because the

26. 

Researchers wish to determine if a new experimental medication will reduce the symptoms of allergy sufferers without the side effect of drowsiness. To investigate this question, the researchers give the new medication to 50 adult volunteers who suffer from allergies. Forty-four of these volunteers report a significant reduction in their allergy symptoms without any drowsiness. This study could be improved by

27. 

Will a fluoride mouthwash used after brushing reduce cavities? Twenty sets of twins were used to investigate this question. One member of each set of twins used the mouthwash after each brushing, the other did not. After six months, the difference in the number of cavities of those using the mouthwash was compared with the number of those who did not use the mouthwash. This experiment uses

28. 

A study examined the effect of garlic on blood cholesterol levels. A total of 192 subjects with starting LDL (“bad cholesterol”) levels between 130 and 190 mg/dl were randomly assigned to one of four treatments for six months: raw garlic eaten daily, a powdered garlic supplement taken daily (Garlicin brand), an aged-garlic extract taken daily (Kyolic brand), or a placebo pill taken daily. The study found no significant or clinical differences in blood cholesterol levels between the four groups at the end of the study. This study uses the principles of

29. 

A population has an equal proportion of males and females. That is, when randomly selecting one individual, the probability that the individual is male (M) is 1/2 and the probability that the individual is female (F) is 1/2. In the first 50 randomly selected individuals, 20 were male. In the next 50 randomly selected individuals, which of the following must happen?

30. 

The Centers for Disease Control and Prevention receives information about the causes for HIV/AIDS infection in the United States. Here are the causes of infection and their respective probability among American women ages 20 to 24 years old.

The probability that an American woman age 20 to 24 contracted HIV/AIDS either via heterosexual sex or via perinatal infection is

31. 

Based on a recent Gallup survey, we define the following probability model for the number X of daily cups of coffee consumed by Americans.

The probability that an American does not consume 2 cups of coffee daily is _______ .

32. 

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

33. 

The frequency of color blindness (dyschromatopsia) in the Caucasian American male population is estimated to be about 8%. Let's call X the number of color-blind individuals in a random sample of 8 Caucasian American males. The table below gives the probability distribution for X.

What is the probability of getting 1 or 2 color-blind individuals in the sample?

34. 

Using the standard Normal distribution tables, the area under the standard Normal curve corresponding to Z > –2.62 is

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?

36. 

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

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. To ensure that the shortest 8% of the brook trout get thrown back, the lower cut-off should be set at

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

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

40. 

A national survey by Gallup interviewed 1014 adults and found that they had consumed on average 4.2 alcoholic beverages in the past seven days.   Considering a sample of 1014 adults a large sample, which of the following is TRUE?

41. 

The fact that the sample mean doesn't tend to over- or under-estimate the population mean makes the sample mean

42. 

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

43. 

The variability of a statistic is described by the

44. 

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. You take water specimens from 4 randomly selected locations on this river basin. Use the 68–95–99.7 rule to answer this question. What is the range of average pH measurements that make up roughly the middle 95% of the sampling distribution for random samples of 4 specimens?

45. 

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. If you take a random sample of 25 adult men with liver cirrhosis, what is the probability that their average total body protein is between 9.75 and 9.85 kg?

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