Stats midterm

The caffeine content of 8-ounce cans of a certain cola drink is approximately normally distributed with mean 33 milligrams (mg). A randomly selected 8-ounce can containing 35mg of caffeine is 1.2 standard deviations above the mean. Approximately what percent of 8-ounce cans of the cola have a caffeine content greater than 35mg? a. 1% b. 8% c. 12% d. 16% e. 99%

12%

Under which of the following conditions is it preferable to use stratified random sampling rather than simple random sampling? a. The population can be divided into a small number of strata so that each stratum contains a large number of individuals. b. The population can be divided into strata so that the individuals in each stratum are as much alike as possible. c. The population can be divided into strata so that the individuals in each stratum are as different as possible. e. The population can be divided into strata of equal sizes so that each individual in the population still has the same chance of being selected.

The population can be divided into strata so that the individuals in each stratum are as much alike as possible.

In a parking lot with 200 cars, 50 cars are white, 30 cars are red, and 20 cars are silver. One car will be selected at random from the parking lot. If each car in the parking has only one color, which of the following cannot be the probability that the selected car will be green? a. 0 b. 0.1 c. 0.2 d. 0.5 e. 0.6

.6

Opinion-polling organizations contact their respondents by sampling random telephone numbers. Assume that interviewers can now reach about 71% of U.S. households, while the percentage of those contacted who agree to cooperate with the survey is 31%. Each household, it can be safely assumed, is independent of the others. What is the probability of failing to contact a household or of contacting the household but not getting them to agree to the interview? a. 0.20 b. 0.50 c. 0.51 d. 0.78 e. 0.80

.78

A large store has a customer service department where customers can go to ask for help with store-related issues. According to store records, approximately ¼ of all customers who go to the service department ask for help finding an item. Assume the reason each customer goes to the service department is independent from customer to customer. Based on the approximation, what is the probability that at least 1 of the next 4 customers who go to the service department will ask for help finding an item? A. 4 1/4 B. 1 - (1/4)^4 C. 1 - (3/4)^4 D. 4 (1/4)^4 (3/4)^3 E. (3/4) (3/4) (2/4) (1/4)

1 - (3/4)^4

Shalise competed in a jigsaw puzzle competition where participants are timed on how long they take to complete puzzles of various sizes. Shalise completed a small puzzle in 75 minutes and a large jigsaw puzzle in 140 minutes. For all participants, the distribution of completion time for the small puzzle was approximately normal with mean 60 minutes and standard deviation 15 minutes. The distribution of completion time for the large puzzle was approximately normal with mean 18p minutes and standard deviation 40 minutes. Approximately what percent of the participants had finishing times greater than Shalise's for each puzzle? a. 16% on the small puzzle and 16% on the large puzzle b. 16% on the small puzzle and 84% on the large puzzle c. 32% on the small puzzle and 68% on the large puzzle d. 84% on the small puzzle and 84% on the large puzzle e. 84% on the small puzzle and 16% on the large puzzle

16% on the small puzzle and 84% on the large puzzle

A fair coin has come up 'heads' 10 times in a row. The probability that the coin will come up heads on the next flip is... a. 50%. b. 100%. c. greater than 50%, since it appears that we are in a streak of 'heads.' d. less than 50%, since 'tails' is due to come up. e. it can not be determined.

50%

A candy company produces individually wrapped candles. THe quality control manager for the company believes that the weight of the candies is approximately normally distributed with mean 720 milligrams (mg). If the manager's belief is correct, which of the following intervals of weights will contain the largest proportion of the candles in the distribution of weights? a. 740 mg to 780 mg b. 700 mg to 740 mg c. 680 mg to 720 mg d. 660 mg to 700 mg e. 620 mg to 660 mg

700 mg to 740 mg

Measurements of water quality were taken from a river downstream from an abandoned chemical dumpsite. Concentrations of a certain chemical were obtained from 9 measurements taken at the surface of the water, 9 measurements taken at mid-depth of the water, and 9 measurements taken at the bottom of the water. What type of study was conducted, and what is the response variable of the study? a. An experiment was conducted, and the response variable is the concentration of the chemical. b. An experiment was conducted, and the response variable is the depth of the water. c. A census was conducted, and the response variable is the depth of the water. d. An observational study was conducted, and the response variable is the concentration of the chemical. e. An observational study was conducted, and the response variable is the depth of the water.

An observational study was conducted, and the response variable is the concentration of the chemical

A company determines the mean and standard deviation of the number of sick days taken by its employees in one year. Which of the following is the best description of the standard deviation? a. Approximately the mean distance between the number of sick days taken by individual employees and the mean number of sick days taken by all employees b. Approximately the median distance between the number of sick days taken by individual employees and the median number of sick days taken by all employees c. The distance between the greatest number of sick days taken by an employee and the mean number of sick days taken by all employees d. The number of days separating the fewest sick days taken and the most sick days taken when considering all employees e. The number of days separating the fewest sick days taken and the most sick days taken when considering the middle 50 percent of the distribution

Approximately the mean distance between the number of sick days taken by individual employees and the mean number of sick days taken by all employees

A botanist found a correlation between the length of an aspen leaf and its surface area to be 0.94. Why does the correlation value of 0.94 not necessarily indicate that a linear model is the most appropriate model for the relationship between the length of an aspen leaf and its surface area? a. The value must be exactly 1 or -1 to indicate a linear model is the most appropriate model. b. The value must be 0 to indicate a linear model is the most appropriate model. c. A casual relationship should be established first before determining the most appropriate model. d. The value of 0.94 implies that on 88% of the data have a linear relationship. e. Even with a correlation value of 0.94, it is possible that the relationship could still be better represented by a nonlinear model.

Even with a correlation value of 0.94, it is possible that the relationship could still be better represented by a nonlinear model.

The SC Electric Company has bid on two electrical wiring jobs. The owner of the company believes that If the owner's beliefs are correct, which of the following statements must be true concerning event A and event B? The probability of being awarded their first job (event A) is .75 The probability of being awarded their second job (event B) .5 The probability of being awarded both jobs (event A & B) .375 a. Event A and event B are mutually exclusive and are independent. b. Event A and event B are mutually exclusive and are not independent. c. Event A and event B are not mutually exclusive and are independent. d. Event A and event B are not mutually exclusive and are not independent. e. Event A and event B are not mutually exclusive, and independence cannot be determined with the information given.

Event A and event B are not mutually exclusive and are independent

Based on the scatterplots, for which gender does there appear to be evidence that the more time a lion cub spends playing, the sooner the cub is likely to begin hunting? a. For female cubs only b. For male cubs only c. For both male cubs and female cubs, with equal evidence d. For both male cubs and female cubs, with more evidence for female cubs than male cubs e. For neither male cubs nor female cubs

For female cubs only

Gina's doctor told her that the standardized score (z-score) for her systolic blood pressure, as compared to the blood pressure of other women her age, is 1.50. Which of the following is the best interpretation of this standardized score? a. Gina's systolic blood pressure is 150 b. Gina's systolic blood pressure is 1.50 standard deviations above the average systolic blood pressure of women her age c. Gina's systolic blood pressure is 1.50 above the average systolic blood pressure of women her age d. Gina's systolic blood pressure is 1.50 times the average systolic blood pressure for women her age e. Only 1.5% of women Gina's age have a higher systolic blood pressure than she does

Gina's systolic blood pressure is 1.50 standard deviations above the average systolic blood pressure of women her age

A researcher wanted to study the effects of a certain chemical on cell growth. The chemical was to be applied at two different doses, high and low, to two different cell types, strain A and strain B. Each combination of dose and cell type was to be replicated ten times. To have consistency from one replicate to the next, the researcher decided to use four lab technicians. One technician would be assigned the high dose with strain A. A second would be assigned the low dose with strain B. A third would be assigned the high dose with strain B. A fourth would be assigned the low dose with strain B. The assignment of lab technicians to the replicates for a combination of doses and cell type would be randomized. A statistician told the researcher that the design could be improved by controlling confounding variables. Which of the following is potentially a confounding variable in this study? a. Chemical Used b. Lab Technician c. Dose d. Cell Type e. Cell Growth

Lab technician

A high school teacher has 78 students. Of those students, 35 are in the band and 32 are on a sports team. There are 16 students who are not in the band or on a sports team. One student from the 78 students will be selected at random. Let event B represent the event of selecting a student in the band, and let event S represent the event of selecting a student on a sports team. Are B and S mutually exclusive events? a. No, because P(B ⋂ S) = 5/78 b. No, because P(B ⋂ S) = 48/78 c. No, because P(B ⋂ S) = 62/78 d. Yes, because P(B ⋂ S) = 5/78 e. Yes, because P(B ⋂ S) = 62/78

No, because P(B ⋂ S) = 5/78

An experiment will be conducted to determine whether children learn their multiplication facts better by practicing with flash cards or by practicing on a computer. Children who volunteer for the experiment will be randomly assigned to one of the two treatments. After practice, the children will be given a test on their multiplication facts. Why will it be impossible to conduct a double-blind experiment? a. The experimenter will know whether the child is a boy or a girl and whether he or she used flash cards or the computer. b. The child will know whether he or she is a boy or a girl. c. The child will know whether he or she used flash cards or the computer. d. The person who grades the test will know whether the child was a boy or a girl. e. The person who grades the tests will know whether the child used flash cards or the computer.

The child will know whether he or she used flash cards or the computer

A graph (not shown) of the selling of homes in a certain city for the month of April reveals that the distribution is skewed to the left. Which of the following statements is the most reasonable conclusion about the selling prices based on the graph? a. The mean is greater than the median b. The median is the average of the first quartile and the third quartile c. There are fewer selling prices between the first quartile and the median than there are between the median and the third quartile d. There are more selling prices that are less than the mean than selling prices that are greater than the mean e. The value of the maximum minus third quartile is less than the value of first quartile minus minimum

The value of the maximum minus third quartile is less than the value of first quartile minus minimum

Suppose a roadrunner has a total length of 59.0 cm and tail length of 31.1 cm. Based on the residual, does the regression model overestimate or underestimate the tail length of the roadrunner? a. Underestimate, because the residual is positive. b. Underestimate, because the residual is negative. c. Overestimate, because the residual is positive. d. Overestimate, because the residual is negative. e. Neither, because the residual is 0.

Underestimate, because the residual is positive.

The distributions of four variables are shown in the following table histograms. Which of the following shapes is NOT represented by one of the four distributions? a. Uniform b. Bimodal c. Skewed to the left d. Skewed to the right e. Symmetric and unimodal

Uniform