AP Stat Vocabulary

Question 1

Individuals

Answer 1

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

Question 2

Variable

Answer 2

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

Question 3

Categorical Variable

Answer 3

places an individual into several groups of categories

Question 4

Quantitative Variable

Answer 4

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

Question 5

Distribution

Answer 5

The ___ of a variable tells us what values the variable takes and how often to take these values

Question 6

Pie Chart

Answer 6

Chart that 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 7

Bar Graph

Answer 7

Graph 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.

Question 8

Two-Way Table

Answer 8

Table of counts that organizes data about two categorical variables.

Question 9

Marginal Distribution

Answer 9

the ___ 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 10

Conditional Distribution

Answer 10

A ____ of a variable describes the values of that 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 11

Segmented Bar Graph

Answer 11

Graph 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 12

Association

Answer 12

There is an _____ between two variables if knowing the value of one variable helps predict the value of the other. If knowing the value of one variable does not help you predict the value of the other, then there is no association between the variables.

Question 13

Side-by-Side Bar Graph

Answer 13

Graph 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 14

Frequency Table

Answer 14

Table that displays the count (frequency) of observations in each category or class.

Question 15

Relative Frequency Table

Answer 15

Table that shows the percents (relative frequencies) of observations in each category or class.

Question 16

Roundoff Error

Answer 16

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

Question 17

Dotplot

Answer 17

Simple graph that shows each data value as a dot above

its location on a number line.

Question 18

Shape

Answer 18

When describing a distribution ___ look at the main features. Look for major peaks, clusters of values and obvious gaps, potential outliers, rough symmetry, or clear skewness

Question 19

Symmetric (distribution)

Answer 19

A graph in which the right and left sides are approximately mirror images of each other.

Question 20

Skewed Right

Answer 20

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.

Question 21

Skewed Left

Answer 21

It is skewed to the left if the left side of the graph is much longer than the right side.

Question 22

Unimodal

Answer 22

A graph of quantitative data with a single peak.

Question 23

Bimodal

Answer 23

A graph of quantitative data with two clear peaks.

Question 24

Multimodal

Answer 24

A graph of quantitative data with more than two

clear peaks.

Question 25

Stemplot

Answer 25

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.

Question 26

Splitting Stems

Answer 26

Method for spreading out a stemplot that has too

few stems.

Question 27

Back-to-Back Stemplots

Answer 27

Plot 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 28

Histogram

Answer 28

Graph that 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 29

Mode

Answer 29

Value or class in a statistical distribution having the greatest frequency.

Question 30

Center

Answer 30

The center is the median and/or mean of the data.

Question 31

Spread

Answer 31

The range of data

Question 32

Range

Answer 32

The maximum value minus the minimum value for a set

of quantitative data.

Question 33

Outliers

Answer 33

Individual value that falls outside the overall pattern of a

distribution.

Question 34

Mean

Answer 34

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

Question 35

Median

Answer 35

The midpoint of a distribution; the number such that about half the observations are smaller and about 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 is the center observation in the ordered list. (3) If the number of observations n is even, the median is the average of the two center observations in the ordered list.

Question 36

Inference

Answer 36

Drawing conclusions that go beyond the data at hand.

Question 37

Interquartile Range

Answer 37

IQR = Q3 – Q1.

Question 38

Five Number Summary

Answer 38

Smallest observation, first quartile, median, third quartile, and largest observation, written in order from smallest to largest.
In symbols: Minimum Q1 Median Q3 Maximum

Question 39

Boxplot

Answer 39

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 smallest and largest observations that are not outliers. Outliers are marked with a special symbol such as
an asterisk

Question 40

Standard Deviation

Answer 40

Statistic that measures the typical distance of the values in a distribution from the mean. It is calculated by finding an “average” of the squared distances and then taking the square root.

Question 41

Variance

Answer 41

“Average” squared deviation of the observations in a data set from their mean. In symbols,

Question 42

Census

Answer 42

Study that attempts to collect data from every individual

in the population.

Question 43

Continuous Variable

Answer 43

Variable that takes all values in an interval of numbers. The probability distribution of a continuous random variable is described by a density curve.
The probability of any event is the area under the density curve and above the values of the variable that make up the event.

Question 44

Discrete Variable

Answer 44

Takes a fixed set of possible values with
gaps between. The probability distribution of a discrete random variable gives its possible values and their probabilities.
The probability of any event is the sum of the probabilities for the values of the variable that make up the event.

Question 45

Univariate Data

Answer 45

When we conduct a study that looks at only one variable, we say that we are working with univariate data. Suppose, for example, that we conducted a survey to estimate the average weight of high school students. Since we are only working with one variable (weight), we would be working with univariate data

Question 46

Bivariate Data

Answer 46

When we conduct a study that examines the relationship between two variables, we are working with bivariate data. Suppose we conducted a study to see if there were a relationship between the height and weight of high school students. Since we are working with two variables (height and weight), we would be working with bivariate data

Question 47

Population

Answer 47

In a statistical study, the entire group of individuals

we want information about.

Question 48

Sample

Answer 48

Subset of individuals in the population from which we

actually collect data.

Question 49

Simpson’s Paradox

Answer 49

when averages are taken across different groups, they can appear to contradict the overall averages