Frequency Distribution (Tezlik paylanması)
We begin the discussion of how tabular and graphical methods can be used to summarize
c ategorical data with the definition of a frequency distribution.
Let us use the following example to demonstrate the construction and interpretation of
a frequency distribution for categorical data. Coke Classic, Diet Coke, Dr. Pepper, Pepsi,
and Sprite are five popular soft drinks. Assume that the data in Table 2.1 show the soft drink
selected in a sample of 50 soft drink purchases.
To develop a frequency distribution for these data, we count the number of times each
soft drink appears in Table 2.1. Coke Classic appears 19 times, Diet Coke appears 8 times,
Dr. Pepper appears 5 times, Pepsi appears 13 times, and Sprite appears 5 times. These counts
are summarized in the frequency distribution in Table 2.2.
İzah: Tezlik paylanması bir göstəricinin neçə dəfə təkrarlanmasıdır.
This frequency distribution provides a summary of how the 50 soft drink purchases are distributed across the five soft drinks. This summary offers more insight than the original data shown in Table 2.1. Viewing the frequency distribution, we see that Coke Classic is the leader, Pepsi is second, Diet Coke is third, and Sprite and Dr. Pepper are tied for fourth. The frequency distribution summarizes information about the popularity of the five soft drinks.
Relative Frequency and Percent Frequency Distributions
A frequency distribution shows the number (frequency) of items in each of several nonoverlapping classes. However, we are often interested in the proportion, or percentage, of items in each class. The relative frequency of a class equals the fraction or proportion of items belonging to a class. For a data set with n observations, the relative frequency of each class can be determined as follows:
The percent frequency of a class is the relative frequency multiplied by 100. A relative frequency distribution gives a tabular summary of data showing the relative frequency for each class. A percent frequency distribution summarizes the percent frequency of the data for each class.Table 2.3 shows a relative frequency distribution and a percent frequency distribution for the soft drink data. In Table 2.3 we see that the relative frequency for Coke Classic is 19/50 = .38, the relative frequency for Diet Coke is 8/50 =.16, and so on. From the percent frequency distribution, we see that 38% of the purchases were Coke Classic, 16% of the purchases were Diet Coke, and so on.We can also note that 38% +26%16%=80% of the purchases were the top three soft drinks.
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