Statistics Chapter 2

Variable

A characteristic that varies from one person or thing to another.

Pie chart

A disk divided into wedge-shaped pieces proportional to the relative frequencies of the qualitative data.

Discrete variable

A variable whose possible values can be listed, even though the list may continue indefinitely. A discrete variable usually involves a count of something. EX: number of cars, siblings etc...

Continuous variable

A variable whose possible values form some interval of numbers. Usually involves a measurement of something, such as the height of a person, weight of a newborn, etc...

Continuous data

Values of a continuous variable.

Constructing a relative frequency distribution of qualitative data

1) Obtain a frequency distribution of the data 2) Divide each frequency by the total number of observations.

Frequency distribution

A listing of the distinct values and their frequencies.

Relative frequency distribution of qualitative data

A listing of the distinct values and their relative frequencies.

Observation

An individual piece of data.

Histogram

Displays the classes of the quantative data on a horizontal axis and the frequencies (relative frequencies, percents) of those classes on a vertical axis. The frequency (relative frequency, percent) of each class is represented by a vertical bar whose height is equal to the frequency (relative frequency, percent) of that class. The bars should touch each other.

Distribution of a data set

Is a table, graph or formula that provides the values and how often they occur.

Descriptive statistics

Methods for organizing and summarizing information.

Class mark

The average of the two class limits of a class.

Class midpoint

The average of the two cut points of a class.

Data set

The collection of all observations for a particular variable is called a data set.

Class width

The difference between the cut points of a class

Class width

The difference between the lower limit of a class and the lower limit of the next higher class.

Upper class limit

The largest value that could go into a class.

Frequency

The number of times a particular distinct value occurs.

Relative frequency

The ratio of the frequency to the total number of observations. It is just a percentage expressed as a decimal.

Lower class cutpoint

The smallest value that could go in a class.

Upper class cutpoint

The smallest value that could go in the next higher class (equivalent to the lower cut point of the next higher class.)

Lower class limit

The smallest value that could go into a class.

Sample data

The values of a variable for a sample of the population.

Population data

The values of a variable for the entire population

Discrete data

Values of a discrete variable.

Qualitative data

Values of a qualitative variable

Quantitative data

Values of a quantitative variable

Data

Values of a variable

Qualitative variables

Variables that yield nonnumerical information.

Quantitative variables

Variables that yield numerical information.