What is a bar diagram and give an example in drawing?

Bar Charts. A graph very similar to a histogram is the bar chart. Bar charts are often used for qualitative or categorical data, although they can be used quite effectively with quantitative data if the number of unique scores in the data set is not large. A bar chart plots the number of times a particular value or category occurs in a data set, with the height of the bar representing the number of observations with that score or in that category. The Y-axis could represent any measurement unit: relative frequency, raw count, percent, or whatever else is appropriate for the situation. For example, the bar chart in Figure 4.3 plots the number of people, in millions, belonging in one of the four major ethnic categories in the United States in 1990. Figure 4.3 Ethnic category is a qualitative or categorical variable. You can see that most of the U.S. population is "White." Bar charts can be used quite effectively with quantitative data as well but some problems occur. Figure 4.4 shows a bar chart of the sex partners data. Figure 4.4 A bar chart of the "number of sex partners last year" variable. Most computer programs that generate bar charts will treat each quantitative score as a category. What this means is that the bar chart may not space out the scores appropriately on the X axis of the chart. As you can see in Figure 4.4, SPSS ignores the fact that there are no 9s and no observations with values between 11 and 13. As a result, it places "8" and "10" right next to each other, and then places "14" next to "10." It simply treats these scores with no observations as impossible. As a result, looking at a bar chart can give a misrepresentation as to the shape of the distribution. Second, if there are many unique scores in the data set, each of which occurs infrequently, a bar chart may provide no additional information than could be obtained from just looking at the data set. For example, imagine a bar chart of the following data: 4.3, 6.5, 1.2, 6.9, 4.1, 0.4, 6.1, 3.6, 1.6, 2.3. There is only one of every score. So a bar chart would provide little information because it would just display 10 bars equal in height (i.e., with a height of 1).