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Unformatted text preview: Descriptive Statistics Chapters 2 through 4 cover Descriptive Statistics After we collect the raw data (from a sample survey or a designed experiment), we can Describe the data using visual methods (charts, etc.) Describe the data using numeric methods (averages, etc.) Different methods are appropriate for different types of data Fall 2008 1 Chapter 2 Organizing and Summarizing Data Fall 2008 2 Chapter 2 Organizing and Summarizing DATA Section 1 Organizing Qualitative Data Fall 2008 3 Organizing Qualitative Data Constructing a Frequency Distribution Raw qualitative data comes as a list of values each value is one out of a set of categories These values can be organized as either a long list or in a table Raw qualitative data comes as a list of values each value is one out of a set of categories These values can be organized as either a long list or in a table Interpreting the list of data can be difficult, particularly if there is a lot of data Methods are needed to aid interpretation Fall 2008 4 Organizing Qualitative Data Constructing a Frequency Distribution Qualitative data values can be organized by a frequency distribution A frequency distribution is a table that lists Each of the categories The frequency, or the count, for each category Fall 2008 5 Organizing Qualitative Data Constructing a Frequency Distribution A simple data set is blue, blue, green, red, red, blue, red, blue A frequency table for this qualitative data is The most commonly occurring color is ______ Color Frequency Blue ? Green ? Red ? Fall 2008 6 Organizing Qualitative Data Constructing a Relative Frequency Distribution The frequencies are the counts of the observations The frequencies are the counts of the observations The relative frequencies are the proportions (or percents) of the observations out of the total The frequencies are the counts of the observations The relative frequencies are the proportions (or percents) of the observations out of the total A relative frequency distribution lists Each of the categories The relative frequency for each category Fall 2008 7 Organizing Qualitative Data Constructing a Relative Frequency Distribution Use the same simple set of data blue, blue, green, red, red, blue, red, blue A relative frequency table is computed as follows Sum of all frequencies = _____ Blue has a relative frequency of _______ Green has a relative frequency of _______ Red has a relative frequency of _______ Fall 2008 8 Organizing Qualitative Data Constructing a Frequency Distribution A relative frequency table for this qualitative data is A relative frequency table can also be constructed with percents Color Relative Frequency Blue ?...
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