Graphs, Charts, and Tables - Describing Your Data ©

Frequency Distributions frequency distribution A frequency distribution is the sum of a set of data that displays the number of observations in each of the distributions distinct categories or classes.

Frequency Distribution of Years in College (Figure 2-1)

Relative Frequency relative frequency The relative frequency is the proportion of total observations contained in a given category.

Relative Frequency Distribution of Years in College (Figure 2-3)

Grouping Data Into Classes 4 Continuous data : Data whose possible values are uncountable and which may assume any value in an interval. 4 Data array : Data that have been sorted in ascending or descending order. 4 Mutually exclusive classes : Classes that do not overlap. 4 All inclusive classes : A set of classes that contains all the possible values. 4 Equal width classes : Distance between lowest possible value and highest possible value in each class is the same.

Steps for Grouping Data Into Classes 4 Step 1: Determine the number of groups or classes to use. 4 Step 2: Establish the class width.

Class Width

Steps for Grouping Data Into Classes 4 Step 1: Determine the number of groups or classes to use. 4 Step 2: Establish the class width. 4 Step 3: Determine the class boundaries for each class.

Steps for Grouping Data Into Classes 4 Step 1: Determine the number of groups or classes to use. 4 Step 2: Establish the class width. 4 Step 3: Determine the class boundaries for each class. 4 Step 4: Count the number of values in each class.

Frequency Histograms (Figure 1-2)

Frequency Histograms A histogram shows three general types of information: 4 It provides visual indication of where the approximate center if the data is. 4 We can gain an understanding of the degree of spread, or variation, in the data. 4 We can observe the shape of the distribution.

Histograms Showing Different Centers

Histograms - Same Center, Different Spread