Deck 3: Finding Relationships Among Variables

Question 1

An example of a joint category of two variables is the count of all non-drinkers who are also nonsmokers.

Answer 1

True

Question 2

Comparing a numerical variable across two or more subpopulations is known as a comparison problem.

Answer 2

True

Question 3

Correlation is not useful for describing the strength and direction of nonlinear relationships.

Answer 3

True

Question 4

The correlation between two variables is unitless and always between -1 and +1.

Question 5

Correlation is a single-number summary of a scatterplot.

Question 6

Strongly related variables may have a correlation close to zero if the relationship is nonlinear.

Question 7

Counts for a categorical variable are often expressed as percentages of the total.

Question 8

The scatterplot is a graphical technique used to display the relationship between two numerical variables.

Question 9

A trend line on a scatterplot is a line or a curve that "fits" the scatter as well as possible.

Question 10

We cannot attempt to interpret correlations numerically,with the one possible exception of indicating whether they are positive or negative.

Question 11

If the standard deviations of X and Y are 15.5 and 10.8,respectively,and the covariance of X and Y is 128.8,then the correlation coefficient is approximately 0.77.

Question 12

We can use side-by-side boxplots to compare at most 2 distributions of numeric data.

Question 13

The advantage that correlation has over covariance is that correlation has a set lower and upper limit.

Question 14

Correlation is affected by the measurement scales applied to the X and Y variables.

Question 15

If the standard deviation of X is 15,the covariance of X and Y is 94.5,and the correlation is 0.90,then the variance of Y is 7.0.

Question 16

The cutoff for defining a large correlation is 0.5.

Question 17

To form a scatterplot of X versus Y,X and Y must be paired variables.

Question 18

Side-by-side box plots allow you to quickly see how two or more categories of a numerical variable compare.

Question 19

If the coefficient of correlation r = 0 .80,the standard deviations of X and Y are 20 and 25,respectively,then Cov(X,Y)must be 400.

Question 20

Correlation and covariance can be used to examine relationships between numeric variables as well as for categorical variables that have been coded numerically.

Question 21

To examine relationships between two categorical variables,we can use

A)counts and corresponding charts of the counts.
B)scatter plots.
C)histograms.
D)boxplots.

Question 22

Tables used to display counts of a categorical variable are called

A)crosstabs.
B)contingency tables.
C)either crosstabs or contingency tables.
D)neither crosstabs nor contingency tables.

Question 23

Relationships between two variables are less evident when counts are expressed as percentages of row totals or column totals.

Question 24

Examples of comparison problems include

A)salary broken down by male and female subpopulations.
B)cost of living broken down by region of a country.
C)recovery rate for a disease broken down by patients who have taken a drug and patients who have taken a placebo.
D)all of these choices.

Question 25

Displaying all correlations between 0.6 and 0.999 on a scatterplot as green and all correlations between -1.0 and -0.6 as red is known as _____ formatting.

A)rank-order
B)categorical
C)conditional
D)numerical

Question 26

We study relationships among numerical variables using

A)pie charts.
B)counts.
C)scatterplot charts.
D)percentages.

Question 27

One characteristic of "paired variables" is that

A)one variable is a negative value and the other is a positive value.
B)both variables are positive values.
C)each variable has the same number of observations.
D)each variable has a different number of observations.

Question 28

The limitation of covariance as a descriptive measure of association is that it

A)only captures positive relationships.
B)does not capture the units of the variables.
C)is very sensitive to the units of the variables.
D)is invalid if one of the variables is categorical.

Question 29

Which correlation coefficient suggests the strongest relationship?

A)+1
B)-1
C)0
D)+0.5

Question 30

Correlation and covariance measure the

A)strength of a linear relationship between two numerical variables.
B)direction of a linear relationship between two numerical variables.
C)strength and direction of a linear relationship between two numerical variables.
D)strength and direction of a linear relationship between two categorical variables.

Question 31

Which of the following are considered numerical summary measures?

A)Mean and variance
B)Variance and correlation
C)Correlation and covariance
D)Covariance and variance

Question 32

Statisticians often refer to the pivot tables that display counts as contingency tables or crosstabs.

Question 33

Scatterplots are also referred to as

A)crosstabs.
B)contingency charts.
C)X-Y charts.
D)all of these choices

Question 34

A useful way of comparing the distribution of a numerical variable across categories of some categorical variable is with

A)a side-by-side box plot.
B)a side-by-side pivot table.
C)a side-by-side plot or side-by-side pivot table.
D)neither a side-by-side box plot nor side-by-side pivot table.

Question 35

The most common data format is

A)long.
B)short.
C)stacked.
D)unstacked.

Question 36

If the correlation of variables is close to 0,then we expect to see a(n)_____ on the scatterplot.

A)upward sloping cluster of points
B)downward sloping cluster of points
C)cluster of points around a trendline
D)random scatter of points with no apparent relationship

Question 37

A line or curve superimposed on a scatterplot to quantify an apparent relationship is known as a(n)

A)average.
B)trend line.
C)slope.
D)function.

Question 38

Correlation is useful only for

A)assessing the weakness of a linear relationship.
B)conveying the same information in a simpler format than a scatterplot.
C)measuring the strength of a linear relationship.
D)measuring the strength of a nonlinear relationship.

Question 39

We can infer that there is a strong relationship between two numeric variables when the points on a scatterplot

A)cluster tightly around a straight line.
B)are randomly scattered in no clear pattern.
C)display a positive relationship.
D)display a negative relationship.

Question 40

The filters field of a pivot table contains the data that you want summarized.

Question 41

Approximate the percentage of these Internet users who are in the 58-71 age group.

Question 42

The tables of counts that result from pivot tables are often called

A)samples.
B)sub-tables.
C)populations.
D)crosstabs.

Question 43

What is the average annual salary of the employed Internet users in this sample?

Question 44

Approximate the percentage of these Internet users who are married.

Question 45

Approximate the percentage of these Internet users who are single with no formal education beyond high school.

Question 46

Which two variables have the strongest linear relationship with annual salary?

Question 47

Changing the location of fields in a pivot table is known as

A)slicing.
B)dicing.
C)sorting.
D)pivoting.

Question 48

Approximate the percentage of these Internet users who are currently employed.

Question 49

The four areas of a pivot table are

A)Crosstabs,Fields,Rows,and Columns.
B)Data,Count,Contingency,and Percentage.
C)Filters,Rows,Columns,and Values.
D)Sort,Rows,Columns,and Count.

Question 50

Approximate the percentage of these Internet users who are married with formal education beyond high school.

Question 51

What does a scatterplot illustrate?

A)The median of the variables
B)What type of relationship there is between two variables
C)The percentage of values that fall in a particular category
D)The variability of the middle 50% of the data

Question 52

What percentage of these internet users has formal education beyond high school?

Question 53

Approximate the percentage of these internet users who are women in the 30-43 age group.

Question 54

Approximate the percentage of these internet users who are women.

Question 55

Approximate the percentage of these Internet users who are men under the age of 30.

Question 56

The tool that provides useful information about a data set by breaking it down into categories is a

A)histogram.
B)scatterplot.
C)pivot table.
D)spreadsheet.