CHAPTER 1 TERMS

Question 1

The 1.5 × IQR Rule for Outliers

Answer 1

Call an observation an outlier if it falls more than 1.5 × IQR above the third quartile or below the first quartile.

Question 2

Association

Answer 2

Occurs between two variables if specific values of one variable tend to occur in common with specific values of the other.

Question 3

Back-to-back stemplot (also called a back-to-back stem-and-leaf plot)

Answer 3

Used to compare the distribution of a quantitative variable for two groups. Each observation in both groups is separated into a stem, consisting of all but the final digit, and a leaf, the final digit. The stems are arranged in a vertical column with the smallest at the top. The values from one group are plotted on the left side of the stem and the values from the other group are plotted on the right side of the stem. Each leaf is written in the row next to its stem, with the leaves arranged in increasing order out from the stem.

Question 4

Bar graph

Answer 4

Used to display the distribution of a categorical variable or to compare the sizes of different quantities. The horizontal axis of a bar graph identifies the categories or quantities being compared. Drawn with blank spaces between the bars to separate the items being compared.

Question 5

Bimodal

Answer 5

Describes a graph of quantitative data with two clear peaks.

Question 6

Boxplot

Answer 6

A graph of the five-number summary. The box spans the quartiles and shows the spread of the central half of the distribution. The median is marked within the box. Lines extend from the box to the extremes and show the full spread of the data.

Question 7

Categorical Variable

Answer 7

Places an individual into one of several groups or categories.

Question 8

Conditional distribution

Answer 8

Describes the values of one variable among individuals who have a specific value of another variable. There is a separate conditional distribution for each value of the other variable.

Question 9

Data analysis

Answer 9

A process of describing data using graphs and numerical summaries.

Question 10

Dotplot

Answer 10

A simple graph that shows each data value as a dot above its location on a number line.

Question 11

Distribution

Answer 11

Tells what values a variable takes and how often it takes these values.

Question 12

First quartile Q1

Answer 12

If the observations in a data set are ordered from lowest to highest, the first quartile Q1 is the median of the observations whose position is to the left of the median.

Question 13

The Five-Number Summary

Answer 13

Consists of the smallest observation, the first quartile, the median, the third quartile, and the largest observation, written in order from smallest to largest. In symbols, the five-number summary is Minimum Q1 M Q3 Maximum

Question 14

Frequency table

Answer 14

Displays the count (frequency) of observations in each category or class.

Question 15

Histogram

Answer 15

Displays the distribution of a quantitative variable. The horizontal axis is marked in the units of measurement for the variable. The vertical axis contains the scale of counts or percents. Each bar in the graph represents an equal-width class. The base of the bar covers the class, and the bar height is the class frequency or relative frequency

Question 16

Individuals

Answer 16

Objects described by a set of data. Individuals may be people, animals, or things.

Question 17

Inference

Answer 17

Drawing conclusions that go beyond the data at hand.

Question 18

Interquartile range

Answer 18

IQR = Q3-Q1

Question 19

Marginal distribution

Answer 19

The marginal distribution of one of the categorical variables in a two-way table of counts is the distribution of values of that variable among all individuals described by the table.

Question 20

Mean

Answer 20

The arithmetic average. To find the mean x of a set of observations, add their values and divide by the number of observations.

Question 21

Median M

Answer 21

The midpoint of a distribution, the number such that half the observations are smaller and the other half are larger. To find the median of a distribution: 1. Arrange all observations in order of size, from smallest to largest. 2. If the number of observations n is odd, the median M is the center observation in the ordered list. 3. If the number of observations n is even, the median M is the average of the two center observations in the ordered list.

Question 22

Mode

Answer 22

The value or class in a statistical distribution having the greatest frequency.

Question 23

Multimodal

Answer 23

Describes a graph of quantitative data with more than two clear peaks.

Question 24

Outlier

Answer 24

An individual value that falls outside the overall pattern of a distribution. (AKA: Maria)

Question 25

Overall pattern

Answer 25

In any graph of data, look for the overall pattern and for striking departures from that pattern. Shape, center, and spread describe the overall pattern of the distribution of a quantitative variable.

Question 26

Pie chart

Answer 26

Shows the distribution of a categorical variable as a “pie” whose slices are sized by the counts or percents for the categories. A pie chart must include all the categories that make up a whole.

Question 27

Quantitative Variable

Answer 27

Takes numerical values for which it makes sense to find an average.

Question 28

Range

Answer 28

The range of a set of quantitative data is the maximum value minus the minimum value.

Question 29

Relative frequency table

Answer 29

Shows the percents (relative frequencies) of observations in each category or class.

Question 30

Resistant measure

Answer 30

A statistic that is not affected very much by extreme observations.

Question 31

Roundoff error

Answer 31

The difference between the calculated approximation of a number and its exact mathematical value.

Question 32

Segmented bar graph

Answer 32

Used to compare the distribution of a categorical variable in each of several groups. For each group, there is a single bar with “segments” that correspond to the different values of the categorical variable. The height of each segment is determined by the percent of individuals in the group with that value. Each bar has a total height of 100%.

Question 33

Side by side bar graph

Answer 33

Used to compare the distribution of a categorical variable in each of several groups. For each value of the categorical variable, there is a bar corresponding to each group. The height of each bar is determined by the count or percent of individuals in the group with that value.

Question 34

Simpson’s paradox

Answer 34

An association between two variables that holds for each individual value of a third variable can be changed or even reversed when the data for all values of the third variable are combined.

Question 35

Skewness

Answer 35

A distribution is skewed to the right if the right side of the graph (containing the half of the observations with larger values) is much longer than the left side. It is skewed to the left if the left side of the graph is much longer than the right side.

Question 36

Splitting stems

Answer 36

A method for spreading out a stemplot that has too few stems.

Question 37

Standard deviation sx

Answer 37

Measures the average distance of the observations from their mean. It is calculated by finding an average of the squared distances and then taking the square root .

Question 38

Stemplot (also called a stem-and-leaf plot)

Answer 38

A simple graphical display for fairly small data sets that gives a quick picture of the shape of a distribution while including the actual numerical values in the graph. Each observation is separated into a stem, consisting of all but the final digit, and a leaf, the final digit. The stems are arranged in a vertical column with the smallest at the top. Each leaf is written in the row to the right of its stem, with the leaves arranged in increasing order out from the stem.

Question 39

Symmetry

Answer 39

If the right and left sides of a graph are approximately mirror images of each other.

Question 40

Third quartile Q3

Answer 40

If the observations in a data set are ordered from lowest to highest, the third quartile Q3 is the median of the observations whose position is to the right of the median.

Question 41

Two-way table

Answer 41

A two-way table of counts organizes data about two categorical variables.

Question 42

Unimodal

Answer 42

Describes a graph of quantitative data with a single peak.

Question 43

Variables

Answer 43

Any characteristic of an individual. A variable can take different values for different individuals.

Question 44

Variance sx^2

Answer 44

The average squared distance of the observations in a data set from their mean.