40 terms

Shane_DurkanTEACHER

Individuals

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

Variable

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

Categorical Variable

places an individual into one of several groups or categories.

Quantitative Variable

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

Distribution

The distribution of a variable tells us what values the variable takes and how often it takes these values.

Bar Graph

A graph that uses horizontal or vertical bars to display data

Pie Chart

A form of graph which represents numeric values as segments of a circle.

Two-way Tables

Display visual relationships between the two categorical variables

Marginal Distributions

The Marginal Distributions 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.

Conditional Distribution

A Conditional Distribution 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.

Association

We say that there is an association 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.

Frequency

How often an event happens during a period of time

Side-by-side Bar Graph

A bar graph that compares different groups, in one category, to one another.

Dotplots

Each data is shown as a dot above its location on a number line.

Symmetric

A distribution is roughly symmetric if the right and left sides of the graph are approximately mirror images of each other.

Skewed to the Right

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

Skewed to the Left

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

Shape

The concept of the shape of the distribution refers to the shape of a probability distribution (What are the characteristics of the distribution).

Measures of the Center

Mean and median

Measure of Spread

Used to describe the variability in a sample or population.

Outliers

Numbers that are much greater or much less than the other numbers in the set

Unimodal

A distribution with a single, clearly defined, peak.

Bimodal

A distribution with two clear peaks.

Multimodal

A distribution with more than two clear peaks.

Stemplots

A graphical tool that displays actual numerical values in an ordered fashion using stems and leaves to group the data.

Splitting Stems

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

Back-to-back stemplot

Use this when you want to compare two related distributions.

Histogram

A graph of vertical bars representing the frequency distribution of a set of data.

Mean

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

Median

The midpoint of a distribution, the number such that about half the observations are smaller and about half are larger when arranged in order.

Range

Distance between highest and lowest scores in a set of data.

Interquartile Range

Q3-Q1

First Quartile

Lies one-quarter of the way up the list.

Third Quartile

Lies three-quartiles of the way up the list.

The 1.5 x IQR rule for Outliers

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

The Five Number Summary

Minimum, Q1, M, Q3, Maximum

Box Plot

A graph that displays the highest and lowest quarters of data as whiskers, the middle two quarters of the data as a box, and the median

Standard Deviation

Measures the typical distance of the values in a distribution from the mean.

Standard Deviation (Calculated)

It is calculated by finding an average of the squared deviation and then taking the square root.

Variance

A measure of spread within a distribution (the square of the standard deviation).