Stats midterm
A researcher conducting a telephone survey is concerned about possible sources of bias. Of the following, which is the best example of nonresponse bias. a. The wording of the questions in the survey leads people to respond in a certain way. b. The behavior of the interviewer leads people to respond in a certain way. c. People might be uncomfortable with the survey questions and, as a result, might now always respond to those questions truthfully. d. Many of the people selected to participate in the survey who do not respond might have opinions different from those who do not respond. e. People without telephones are overlooking in the sampling procedure used to determine who is surveyed.
Many of the people selected to participate in the survey who do not respond might have opinions different from those who do not respond.
Which of the following can be used to show a cause-and-effect relationship between two variables? a. A census b. A controlled experiment c. An observational study d. A sample survey e. A cross-sectional survey
A controlled experiment
Dairy farmers are aware there is often a linear relationship between age, in years, of a dairy cow and the amount of milk produced, in gallons per week. The least-squares regression line produced from a random sample is Milk (hat) = 40.8 - 1.1(Age). Based on the model, what is the difference produced between a cow of 5 years and a cow of 10 years? a. A cow of 5 years is predicted to produce 5.5 fewer gallons per week. b. A cow of 5 years is predicted to produce 5.5 more gallons per week. c. A cow of 5 years is predicted to produce 1.1 fewer gallons per week. d. A cow of 5 years is predicted to produce 1.1 more gallons per week. e. A cow of 5 years and a cow of 10 years are both predicted to produce 40.8 gallons per week.
A cow of 5 years is predicted to produce 5.5 more gallons per week.
I. A point with the large residual is an outlier II. A point with high leverage has a y-value that is not consistent with the other y-values in the set III. The removal of an influential point from a data set could change the value of the correlation coefficient Which of the above statements about a least-squares regression analysis is true? a. I only b. II only c. III only d. I and III only e. I, II, and III only
III only
In a certain school district, students from grade 6 through grade 12 can participate in a school-sponsored community service activity. The following bar chart shows the relative frequencies of students from each grade who participate in the community service activity. Which of the following statements is supported by the bar chart? a. The greatest number of participating students was in grade 9. b. The number of participating students in grade 6 was equal to the number of participating students in grade 7. c. The relative frequency of all participating students in grades 6 and 7 combined was 0.60. d. Grade 12 had the least relative frequency of participating students. e. Grade 11 had the greatest relative frequency of participating students.
Grade 12 had the least relative frequency of participating students.
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
Ninety percent of the people who have a particular disease will have a positive result on a given diagnostic test. Ninety percent of the people who do not have the disease will have a negative result on this test. If 5 percent of a certain population has the disease, what percent of that population would test positive for the disease? a. 4.5% b. 5% c. 10% d. 14% e. 90%
14%
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
Some descriptive statistics for a set of test scores are shown below. FOr this test, a certain student has a standardised test score of z = -1.2. What score did this student receive on the test? a. 266.28 b. 779.42 c. 1008.02 d. 1083.38 e. 1311.98
779.42
Sam surveyed 200 students at a school and recorded the eye color and the gender of each student. Of the 80 male students who were surveyed, 60 had brown eyes. If eye color and gender are independent, how many female students surveyed would be expected to have brown eyes? a. 5 b. 20 c. 30 d. 90 e. 100
90
Ice cream question
C
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
A marketing firm obtained random samples of 20 people in five regions of the country to investigate the level of interest in a new product. People in the sample were asked to rate their level of interest on a scale from 1 to 10, with 1 being the least amount of interest and 10 being the greatest. The histograms show the results for each region. The graph for which region displays data for level of interest with the least standard deviation? a. Region A b. Region B c. Region C d. Region D e. Region E
Region D (skewed to the right)
Staff members of a high school newspaper want to obtain an estimate of the average number of years teachers in the state have been teaching. At an education conference attended by many teachers in the state, the staff members randomly selected 50 conference attendees and asked the attendees how long they have been teaching. Which of the following describes the sample and the population to which it would be most reasonable for the staff members to generalize the results? a. The sample is the 50 conference attendees, and the population is all teachers in the state. b. The sample is the 50 conference attendees, and the population is all conference attendees. c. The sample is all conference attendees, and the population is all teachers in the state. d. The sample is all conference attendees. And the population is the 50 conference attendees. e. The sample is the average number of years that all conference attendees have taught, and the population is all conference attendees.
The sample is the 50 conference attendees, and the population is all conference attendees.
A tropical storm is classified as major if it has sustained winds greater than 110 miles per hour. Based on data from the past two decades, a meteorologist estimated the following percentages about future storms.Based on the meteorologist's estimates, approximately what is the probability that a future tropical storm will originate in the Pacific Ocean and be classified as major? 20% of all tropical storms will originate in the AO, of which 20% will be classified as major. 30% of all tropical storms will originate in the EPO, of which 15% will be classified as major. 50% of all tropical storms will originate in the WPO, of which 25% will be classified as major a. 0.045 b. 0.125 c. 0.170 d. 0.400 e. 0.960
.170
A police officer is using a radar device to check motorists' speeds. Prior to beginning the speed check, the officer estimates that 40 percent of motorists will be driving more than 5 miles per hour over the speed limit. Assuming that the police officer's estimate is correct, what is the probability that among 4 randomly selected motorists, the officer will find at least 1 motorist driving more than 5 miles per hour over the speed limit? a. 0.0256 b. 0.1296 c. 0.3456 d. 0.8704 e. 0.9744
0.8704
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
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%
Scientists estimate that the distribution of the life span of the Galapagos Islands giant tortoise is approximately normal with mean 100 years and standard deviation is 15 years. Based on the estimate, which of the following is closest to the age of a Galapagos Islands giant tortoise at the 90th percentile of the distribution? a. 80 years b. 115 years c. 120 years d. 125 years e. 130 years
120 year
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.
D. An observational study was conducted and the response variable was the concentration of the chemical
I. Random scatter in the residuals indicates a model with high predictive power II. If two variables are very strongly associated, then the correlation between them will be near +1.0 or -1.0 III. The higher the correlation between two variables the more likely the association is based in cause and effect Which is true? a. None b. I only c. II only d. I and II only e. I, II, and III
None
At a large airport, data were recorded for one month on how many baggage items were unloaded from each flight upon arrival as well as the time required to deliver all the baggage items on the flight to the baggage claim area. A scatterplot of the two variables indicated a strong, positive linear association between the variables. Which of the following statements is a correct interpretation of the word "strong" in the description of the association? a. A least-squares model predicts that the more baggage items that are unloaded from a flight, the greater the time required to deliver the items to the baggage claim area. b. The actual time required to deliver all the items to the baggage claim area based on the number of items unloaded will be very close to the time predicted by a least-squares model. c. The time required to deliver an item to the baggage claim area is relatively constant, regardless of the number of baggage items unloaded from a flight. d. The variability in time required to deliver all items to the baggage claim area is about the same for all flights, regardless of the number of items unloaded from a flight. e. The time required to unload baggage items from a flight is related to the time required to deliver the items to the baggage claim area.
The actual time required to deliver all the items to the baggage claim area based on the number of items unloaded will be very close to the time predicted by a least-squares model.
Which of the following statements must be true about the data sets A and B displayed in the histograms below? a. The mean of data set A is equal to the mean of data set B. b. The median of data set A is equal to the median of data set B. c. The range of data set A is equal to the range of data set B. d. The standard deviation of data set A is less than the standard deviation of data set B. e. The standard deviation of data set A is greater than the standard deviation of data set B.
The standard deviation of data set A is greater than the standard deviation of data set B.
As part of a science experiment, a student recorded 10 measurements of the temperature of a liquid. One of the measurements was an outlier when compared with the other 9 measurements. Which of the following must be true about the 9 measurements, excluding the outlier, when compared with the 10 measurements? (Note: An outlier is any number that is greater than the upper quartile or less than the lower quartile by at least 1.5 times the interquartile range.) a. The median of the 9 measurements is less than the median of the 10 measurements. b. The median of the 9 measurements is greater than the median of the 10 measurements. c. The maximum of the 9 measurements is less than the maximum of the 10 measurements. d. The maximum of the 9 measurements is greater than the maximum of the 10 measurements. e. The standard deviation of the 9 measurements is less than the standard deviation of the 10 measurements.
The standard deviation of the 9 measurements is less than the standard deviation of the 10 measurements