Statistics_2 - Chapter 2 Chapter 2 Frequency Distributions...

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Chapter 2 Chapter 2: Frequency Distributions and Graphs d Introduction 2–1 Organizing Data 2–2 Histograms, Frequency Polygons, and Ogives 2–3 Other Types of Graphs 2 3 Other Types of Graphs
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Organizing Data Data original form are called raw data , example ( Wealthy People ) 49 57 38 73 81 74 59 76 65 69 54 56 69 68 78 65 85 49 69 61 48 81 68 37 43 78 82 43 64 67 52 56 81 77 79 85 40 85 59 80 60 71 57 61 69 61 83 90 87 74 Little information can be obtained from raw data. Organize these data into class and frequencies, a
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The frequency of a class then is the number of data values contained in a specific class. A frequency distribution is the organization of raw data in table form, using classes and frequencies. Frequency distribution Categorical Frequency Grouped frequency Distributions distribution
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Categorical Frequency Distributions Used for data that can be placed in specific categories, such as nominal or ordinal level data. (political affiliation, religious affiliation) Example ( Blood Types) Twenty five army inductees were given a blood test The data set is A B B AB O O O B AB B B B O A O A O O O AB AB A O B A Construct a frequency distribution O O AB AB A O B A. Construct a frequency distribution. Step 1 Make a table Step 2 Tally the data. Step 3 Count the tallies. d h l Step 4 Find the totals. Step 5 Find the percentage of values in each class % = 100*f/n. Percentages are called relative frequency.
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Grouped Frequency Distributions When the range of the data is large, the data must be grouped into classes For example hours of boat grouped into classes. For example, batteries, . Class limits ( lower limit, Upper limit )
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Class boundaries are used to separate the classes so that there are no gaps in the freq enc distrib tion that there are no gaps in the frequency distribution. For whole numbers, Lower limit 0.5=31 0.5=30.5= lower boundary Upper limit+0.5=37+0.5=37.5= upper boundary If the limits are in tenths, such as 7.8–8.8, the boundaries for that class would be 7.75–8.85 . Class width= lower limit of a class lower limit of the previous class. For example, 31 24=7. The class midpoint .
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For example, Notes: The classes must be mutually exclusive. correct incorrect The classes must be continuous. Even if there are no values in a class. The classes must be exhaustive . There should be enough classes to accommodate all the data. The classes must be equal in width. One exception occurs when a distribution has a class that is open ended. (open ended distribution)
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Step 2 Tally the data. Step 3 Find the numerical frequencies from the tallies the tallies.
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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).
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