Stat 210

Which of the following values represents the strongest correlation between two variables?

-0.92

A random sample of 12 VCU students was chosen and the number of academic credits each is taking this semester and the number of hours of paid work each does each week was determined. The data is given in the table below. Number of credits Hours paid work 15 18 12 14 7 40 16 12 18 0 15 10 12 20 3 36 19 4 18 6 10 30 11 26 What is the value of the correlation coefficient r?

-0.93

A simple random sample of 16 classes being taught at VCU during the fall 2017 semester was selected and for each the number of enrolled students recorded. The data is given below. 63 26 47 48 12 72 52 31 55 126 66 35 22 44 32 37 Calculate the standard deviation of the data.

26.56

A simple random sample of 16 classes being taught at VCU during the fall 2017 semester was selected and for each the number of enrolled students recorded. The data is given below. 63 26 47 48 12 72 52 31 55 126 66 35 22 44 32 37 Calculate the interquartile range of the data.

27.5

A simple random sample of 16 classes being taught at VCU during the fall 2017 semester was selected and for each the number of enrolled students recorded. The data is given below. 63 26 47 48 12 72 52 31 55 126 66 35 22 44 32 37 Calculate the median of the data.

45.5

A simple random sample of 16 classes being taught at VCU during the fall 2017 semester was selected and for each the number of enrolled students recorded. The data is given below. 63 26 47 48 12 72 52 31 55 126 66 35 22 44 32 37 Calculate the mean of the data.

48

A random sample of 12 VCU students was chosen and the number of academic credits each is taking this semester and the number of hours of paid work each does each week was determined. The data is given in the table below. Number of credits Hours paid work 15 18 12 14 7 40 16 12 18 0 15 10 12 20 3 36 19 4 18 6 10 30 11 26 What is the value of the coefficient of determination R2?

0.868

A simple random sample of 16 classes being taught at VCU during the fall 2017 semester was selected and for each the number of enrolled students recorded. The data is given below. 63 26 47 48 12 72 52 31 55 126 66 35 22 44 32 37 Calculate the range of the data.

114

The regression line that gives the linear relationship between the number of academic credits a VCU student is taking this semester and the number of hours of paid work the student does each week is predicted number of paid hours = 50.24 - 2.48(number of academic credits). Suppose Nuria is taking 17 academic credits this semester. Use the regression line to predict the number of hours of paid work a student will do if she is enrolled in 17 academic credits.

8.08

Atlantis Paradise Island is an ocean-themed resort on Paradise Island (Links to an external site.) in the Bahamas (Links to an external site.). Of interest is to determine the proportion of all visitors to the Bahamas in 2019 that spent some time at Atlantis Paradise Island. Based on this information, what is the population of interest?

All visitors to the Bahamas in 2019.

As they board, passengers are asked if they live in the City of Richmond, Henrico County, Chesterfield County, Hanover County, or another location (5 options). The location in which a GRTC Pulse passenger lives is what type of characteristic?

Categorical variable

When describing a distribution, which of the following things must you describe?

Center, spread, shape and unusual features

In partnership with the U.S. Department of Transportation, the Commonwealth of Virginia, the City of Richmond and Henrico County, GRTC and the Project Team launched the GRTC Pulse service on Sunday, June 24, 2018. What type of characteristic is the day GRTC Pulse service was launched?

Constant

Suppose that every day the proportion of all passengers on the GRTC Pulse that are either students or employees of VCU is determined. Based on this, the proportion of daily passengers on the GRTC Pulse who are either students or employees of VCU is what type of characteristic?

Continuous Quantitative Variable

For all passengers who have ridden the GRTC Pulse since service was launched, of interest is to determine the mean age of all the passengers. What type of characteristic is the mean age of all passengers who have ridden the GRTC Pulse?

Continuous Quantitative variable

The regression line that gives the linear relationship between the number of academic credits a VCU student is taking this semester and the number of hours of paid work the student does each week is predicted number of paid hours = 50.24 - 2.48(number of academic credits). Which of the following is the correct interpretation of the intercept of this regression line?

If the number of academic credits is 0 credits, then the predicted number of paid hours of work is 50.24 hours.

An Italian restaurant is interested in comparing a new method for preparing ravioli with the current method. They decide to conduct a study, as described below, to determine which method they will use. The study takes place over a two-week period and involves all customers who order raviolis during that time. With each order, a coin is flipped. If the coin lands on heads, the ravioli is prepared using the new method; if the coin lands on tails, the ravioli is prepared using the current method. After the meal, the customers are given a short, anonymous questionnaire in which they are asked to rate the quality of the ravioli on a scale of 1 to 10 (with larger numbers reflecting higher satisfaction). At the end of two weeks the data are analyzed and the results compared. As described, is this an example of a controlled experiment or an observational study?

Controlled experiment

When describing the relationship between two variables, what things must you describe?

Direction, form and strength

For each GRTC Pulse, the number of stops it makes per day are counted. What type of characteristic is the number of stops for each GRTC Pulse?

Discrete Quantitative variable

What type of characteristic is "number of enrolled students in a class"?

Discrete quantitative variable

Suppose the shape of a stem-and-leaf plot is skewed right. What is the best measure to describe the spread?

Interquartile range

True or false: a stem-and-leaf plot and a histogram are graphical methods for displaying qualitative data.

False

True or false: with two categorical variables we describe the relationship between the two variables by describing the direction, form, and strength of the relationship.

False

Which of the following is a measure of spread that is resistant to outliers?

Interquartile range

Which of the following statistics is a measure of spread that would be resistant to outliers?

Interquartile range

Atlantis Paradise Island is an ocean-themed resort on Paradise Island (Links to an external site.) in the Bahamas (Links to an external site.). Of interest is to determine the proportion of all visitors to the Bahamas in 2019 that spent some time at Atlantis Paradise Island. Based on a brochure published by the resort, the proportion of tourists who visit the Bahamas and spent time at Atlantis Paradise Island is .20. A statement about a population parameter, such as π=.20 is which of the following?

Hypothesis

The regression line that gives the linear relationship between the number of academic credits a VCU student is taking this semester and the number of hours of paid work the student does each week is predicted number of paid hours = 50.24 - 2.48(number of academic credits). Which of the following is the correct interpretation of the slope of this regression line?

If the number of academic credits increases by 1 credit, then the predicted number of paid hours of work decreases by 2.48 hours.

It is believed that older students typically have to work more hours to support themselves (and possibly a family) than younger students. Hence the age of the student affects the relationship between the number of academic credits a VCU student is taking this semester and the number of hours of paid work the student does each week. In this scenario, the age of the student is which of the following?

Lurking variable

Which of the following is a measure of center that would be heavily influenced by outliers?

Mean

Suppose the shape of a stem-and-leaf plot is skewed right. What is the best measure to describe the center?

Median

Which of the following is a measure of center that is resistant to outliers?

Median

A random sample of 85 graduate level classes was selected and the number of enrolled students during the Fall 2017 semester was recorded for each. The data is displayed in the boxplot below. Use this boxplot to completely describe the center of the distribution of the number of enrolled students in this sample of 85 graduate level classes.

Median = 17.5

A sample of 300 passengers who have ridden the GRTC Pulse since service was launched was selected in the following manner. There are a total of 14 GRTC Pulse stations. A random sample of 5 of the 14 GRTC Pulse stations was selected. Then for each of these 5 GRTC Pulse stations (but not the other 9), a random sample of 60 passengers who boarded from that station was selected. What type of sampling procedure is this an example of?

Multistage random sampling

The population of interest is all VCU employees and the parameter of interest is the proportion of all VCU employees who use the GRTC Pulse service. Suppose a sample of 100 VCU employees were randomly selected and contacted, but only 50 of them responded and answered the questions. If the characteristics of those who did respond and those who did not respond are different, what type of bias would this create?

Nonresponse bias

On their website GRTC Pulse lists five different time periods: AM Peak (6:00-9:00 AM), Midday (9:00 AM - 4:00 PM), PM Peak (4:00 - 7:00 PM), Off Peak (7:00 - 11:30 PM), and Late Night (11:30 PM - 6:00 AM). Of interest is to determine which of these five time periods has the highest passenger satisfaction rating. Hence a study was conducted, as follows. A sample of 40 passengers from each time period was selected (40*5 = 200 total passengers), and as they exited the GRTC Pulse they were asked to complete a very short satisfaction survey. The survey results for the passengers in each group were averaged, then the five averages were compared to determine which time period had the highest passenger satisfaction rating. As described, is this an example of a controlled experiment or an observational study?

Observational study

An observation that falls within the range of the other X values but which lies far above or below the regression line and hence produces a large residual is which of the following?

Outlier

Atlantis Paradise Island is an ocean-themed resort on Paradise Island (Links to an external site.) in the Bahamas (Links to an external site.). Of interest is to determine the proportion of all visitors to the Bahamas in 2019 that spent some time at Atlantis Paradise Island. As reported by the department of tourism, the total number of visitors in 2019 was 120,000. In this scenario, is 120,000 an example of a parameter or a statistic?

Parameter

Which of the following is a graphical method of displaying qualitative or categorical variables?

Pie chart

An Italian restaurant is interested in comparing a new method for preparing ravioli with the current method. They decide to conduct a study, as described below, to determine which method they will use. The study takes place over a two-week period and involves all customers who order raviolis during that time. With each order, a coin is flipped. If the coin lands on heads, the ravioli is prepared using the new method; if the coin lands on tails, the ravioli is prepared using the current method. After the meal, the customers are given a short, anonymous questionnaire in which they are asked to rate the quality of the ravioli on a scale of 1 to 10 (with larger numbers reflecting higher satisfaction). At the end of two weeks the data are analyzed and the results compared. As described in the example what is the response variable?

Rating of the quality of ravioli

Which of the following is a graphical method that is used to describe the relationship between two quantitative variables?

Scatterplot

For all passengers who have ridden the GRTC Pulse since service was launched, of interest is to determine the mean age of all the passengers. Suppose a sample of 20 passengers who have ridden the GRTC Pulse since service was launched was selected. The sample is purposely selected such that all 20 passengers were employed by VCU; passengers employed by other agencies and companies are excluded from the sample. In this scenario, what type of bias could this cause?

Selection bias

The main entrees at Chick-fil-A can be grouped into three categories: sandwiches (to include Chick-fil-A Chicken Sandwich, Chick-fil-A Deluxe Sandwich, Spicy Chicken Sandwich, Spicy Deluxe Sandwich, Grilled Chicken Sandwich, and Grilled Chicken Club Sandwich), nuggets/strips (to include Chick-fil-A Nuggets, Chick-n-Strips, and Grilled Nuggets) and wrap (Grilled Chicken Cool Wrap). The Chick-fil-A restaurants are also classified by location, such as Mall, Urban/Downtown, or Suburban. Of interest is to determine if there is a relationship between the category of entrée chosen and the restaurant location. A random sample of 450 orders was analyzed, and the following chart presents the conditional distributions of the category of entrée for each restaurant location. Which of the following is a true statement?

Since the conditional distributions are similar, there is not an association between the category of entrée chosen and the restaurant location.

When describing a distribution, which of the following do you not use?

Size

A random sample of 85 graduate level classes was selected and the number of enrolled students during the Fall 2017 semester was recorded for each. The data is displayed in the boxplot below. Use this boxplot to describe the shape of the distribution of the number of enrolled students in this sample of 85 graduate level classes.

Skewed left

When income/salaries of a collection of people are graphed, the distribution usually has a very long tail to the right because there are a few people who make LOTS of money while most others earn much less. What type of distribution does this describe?

Skewed right

Which of the following is a measure of spread that is influenced by outliers?

Standard deviation

A sample of 400 visitors to the Bahamas in 2019 were selected and each was asked whether they spent some time at Atlantis Paradise Island. In this sample, 120 visitors, or 30%, indicated that they spent some time at Atlantis Paradise Island. In this scenario, is 30% an example of a parameter or a statistic?

Statistic

Suppose a sample of 35 passengers who have ridden the GRTC Pulse since service was launched is selected, as follows. As they board, passengers are asked if they live in the City of Richmond, Henrico County, Chesterfield County, Hanover County, or another location (5 options). A random sample of 7 passengers who have ridden the GRTC Pulse since service was launched was randomly chosen from each of the 5 locations. What type of sampling procedure is this an example of?

Stratified random sampling

This is a concept/definition question: which of the following sampling methods would give the highest likelihood of getting a sample of GRTC Pulse passengers that is representative of all GRTC Pulse passengers in the population?

Stratified random sampling

Which of the following is a correct statement?

The IQR is a measure of spread around the median.

An Italian restaurant is interested in comparing a new method for preparing ravioli with the current method. They decide to conduct a study, as described below, to determine which method they will use. The study takes place over a two-week period and involves all customers who order raviolis during that time. With each order, a coin is flipped. If the coin lands on heads, the ravioli is prepared using the new method; if the coin lands on tails, the ravioli is prepared using the current method. After the meal, the customers are given a short, anonymous questionnaire in which they are asked to rate the quality of the ravioli on a scale of 1 to 10 (with larger numbers reflecting higher satisfaction). At the end of two weeks the data are analyzed and the results compared. As described in the example, what is the treatment?

The method of preparing ravioli

Atlantis Paradise Island is an ocean-themed resort on Paradise Island (Links to an external site.) in the Bahamas (Links to an external site.). Of interest is to determine the proportion of all visitors to the Bahamas in 2019 that spent some time at Atlantis Paradise Island. Based on this information, what is the parameter of interest?

The proportion of all visitors to the Bahamas in 2019 that spent some time at Atlantis Paradise Island

A student computes the correlation coefficient to be r = +1.32. What does this value tell you?

This student either doesn't know what they are doing or made a calculation error (or both).

True or false: With two categorical variables we cannot describe the direction, form and strength of the relationship. Instead we should create a two-way table, a marginal distribution, and then conditional distributions, and compare the conditional distributions to determine if there is a relationship between the two variables or not.

True

True or false: with quantitative variables, to completely describe the relationship between the two variables it is recommended to construct a scatterplot to graphically display the relationship and compute the correlation coefficient to numerically describe the relationship.

True

With stratified random sampling you select at least one subject from every group, while in multistage random sampling you first select some groups and hence subjects are not selected form every group?

True

Of interest is to study the relationship between the number of academic credits a VCU student is taking this semester and the number of hours of paid work the student does each week. Specifically, of interest is to use the number of academic credits the student is taking to predict the number of hours of paid work the student does each week. Based on the information above, which of the following is the correct identification of the independent variable X and the dependent variable Y?

X = number of academic credits a VCU student is taking and Y = number of hours of paid work the student does each week

Of interest is to study the relationship between the number of academic credits a VCU student is taking this semester and the number of hours of paid work the student does each week. Specifically, of interest is to use the number of academic credits the student is taking to predict the number of hours of paid work the student does each week. Based on the information above, which of the following is the independent variable?

number of academic credits a VCU student is taking

Of interest is to study the relationship between the number of academic credits a VCU student is taking this semester and the number of hours of paid work the student does each week. Specifically, of interest is to use the number of academic credits the student is taking to predict the number of hours of paid work the student does each week. Based on the information above, which of the following is the dependent variable?

number of hours of paid work the student does each week