AP Statistics Chapter 1 Vocabulary

1.5 x IQR Rule for Outliers

Low outliers: Q1-1.5(IQR) if values are below, it’s an outlier

High outliers: Q3+1.5(IQR) if values are above, it’s an outlier

Association

Exists between two variables if the value of one variable helps predict the value of the other

Back-to-back stemplot

Stempolot where the leaves on each side are ordered out from a shared/common stem

Bar graph

Shows each category as a bar, with heights showing each frequency or relative frequency

Bimodal

a graph with two clear peaks

Boxplot

Graph made from a five-number summary of a data set; outliers are graphed as points

Categorical Variable

variables that place individuals into groups; favorite color, music genre, state, gender)

Conditional Distribution

Describes the value of a variable among individuals who have a specific value of another variable 

Data analysis

The process of organizing, displaying, summarizing, and questioning data

Distribution

tells us what values a variable takes and how often (frequency)

Dotplot

Shows each data value as a dot above its location on a number line

First quartile (Q1)

In a five-number summary, the value that are one-quarter up on the list of observations; first 25% of the data

Frequency table

A table displaying frequencies/counts in various categories 

Histogram

Shows each interval of values as a bar; heights show frequencies (counts) of relative frequency of each value; quantitative, needs at least five bars to be accurate

Individuals

Objects described by data (the who!)

Inference

A conclusion that goes beyond the given data

Interquartile range (IQR)

The distance between the upper and lower quartiles; IQR = Q3-Q1; very resistant to extreme values

Marginal distribution

the distribution of values of one categorical variable in a two-way table among all individuals described in the table

Mean

An arithmetical average of a distribution; symbol is x̄ (x-bar)

Median

Midpoint of a distribution, usually resistant

Mode

The most frequent value in a distribution

Mosaic plot

A segmented bar graph where the width of the bars is proportional to group size

Multimodal

graph with more than two clear peaks

Outlier

An observation that falls outside the overall pattern of distribution

Overall pattern

Shape, center, spread, outliers of a data set or distribution

Pie chart

A graph that shows each slice (variable) as a part of a whole

Quantitative variable

Takes number values that are quantities; counts are usually measurements like height, income, age, etc.

Range

The largest value of a distribution minus the smallest; shows the spread of data in a single value

Relative frequency

Percentages

Relative frequency table

A table displaying the percentages of certain variables in each category

Resistant measure

A way to measure data that is unaffected or barely affected by extreme values being added

Examples: IQR, median, mode

Roundoff error

When rounding various figures, only to add them and get just short of 100%

Segmented bar graph

Stacks the responses  into a bar that reaches 100% to show the conditional distribution

Side by side bar graph

Used to compare the distributions of multiple different categories to make data easier to interpret

Skewness

Either the right or left side has more data points

Splitting stems

On a stemplot, adding more stems to better organize and interpret data when working with a large data set

Standard deviation

The average distance of values from the mean

Symmetry

The right and left side are approximately mirrored; in a graph, mean and median are the same 

The five-number summary

Used to summarize boxplots: minimum, Q1, median, Q3, maximum values

Variables

Characteristics being measured on an individual

Variance

The value underneath a radical before the root is taken