Chapter 2.1

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# Chapter 2.1 - PowerPoint PPT Presentation

Chapter 2.1. Organizing Data. Raw Data – original form. Distribution of Blood Types of 25 army inductees. Frequency Distribution. A frequency distribution is the organization of raw data in table form, using classes and frequencies.

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### Chapter 2.1

Organizing Data

Raw Data – original form

Distribution of Blood Types of 25 army inductees

Frequency Distribution
• A frequency distribution is the organization of raw data in table form, using classes and frequencies.
• Each raw data value is placed into a quantitative or qualitative category called a class.
• The frequency of a class then is the number of data values contained in a specific class.
Categorical Frequency Distributions
• The categorical frequency distribution is used for data that can be placed in specific categories (nominal and ordinal)
Grouped frequency Distributions
• When the range of the data is large, the data must be grouped into classes that are more than one unit in width, in what is called a grouped frequency distribution.
• Class limits – upper class limit, lower class limit
• Class width – range
• Class boundaries are used to separate the classes so that there are no gaps in the frequency distribution
• There should be between 5 and 20 classes
• It is preferable, but not necessary that the class width be an odd number. This ensures that the midpoint of each class (the class midpoint) has the same place value as the data
• The classes must be mutually exclusive
• The classes must be continuous
• The classes must be exhaustive
• The classes must be equal in width
Ages of the 50 wealthiest people in the world:

Lower Class Limit:

Upper class Limit:

Class width:

Class limits:

These data represent the record high temperatures in degrees Fahrenheit for each of the fifty states

Ungrouped Frequency Distribution
• Used when the range of the data values is relatively small. Uses single data values for each class:
• The data shown represents the number of miles per gallon that 30 selected SUVs obtained in city driving
Cumulative Frequency
• A cumulative frequency distribution is a distribution that shows the number of data values less than or equal to a specific value (usually an upper boundary)
Try it!
• Pg. 45 #1-7