SDS 306 Lecture Notes - Lecture 3: Bar Chart, Categorical Variable, Frequency (Statistics)
25 Jan 2017
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Criteria of a good description: conciseness, understandability, important details. Most detailed description is : raw data but, raw data are neither concise nor understandable. Summarizes data in graphical or pictorial form. Make a picture: helps you think clearly about patterns and relationships hidden in the data table. Make a picture: shows the important features of the data. Make a picture: tells others about the data. The area principle: the area occupied by a part of the graph should correspond to the magnitude of the value it represents. Bars should have equal widths in a bar chart. Be cautious when using two- dimensional pictures to exhibit one-dimensional data. Quantitative variable: e. g. , histograms, stem-and-leaf diagrams. Categorical variable: e. g. , bar and pie charts. For the different values: display the count, frequency or percent. Common methods: frequency tables, relative frequency tables, bar charts, pie charts. A frequency table is a table whose: first column displays each distinct outcome, second column displays that outcome"s frequency.
