# Nearly all distributions can be classified as being

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Nearly all distributions can be classified as being either symmetrical or skewed.In asymmetrical distribution, it is possible to draw a vertical line through the mid-dle so that one side of the distribution is a mirror image of the other (Figure 2.11).In askewed distribution, the scores tend to pile up toward one end of the scale andtaper off gradually at the other end (see Figure 2.11).The section where the scores taper off toward one end of a distribution is called thetailof the distribution.A skewed distribution with the tail on the right-hand side ispositively skewedbecause the tail points toward the positive (above-zero) end of theX-axis. If the tailpoints to the left, the distribution isnegatively skewed(see Figure 2.11).For a very difficult exam, most scores tend to be low, with only a few individuals earn-ing high scores. This produces a positively skewed distribution. Similarly, a very easy examtends to produce a negatively skewed distribution, with most of the students earning highscores and only a few with low values.Not all distributions are perfectly symmetrical or obviously skewed in one direction.Therefore, it is common to modify these descriptions of shape with phrases likely “roughlysymmetrical” or “tends to be positively skewed.” The goal is to provide a general idea ofthe appearance of the distribution.D E FINITIO N SSymmetrical distributionsSkewed distributionsPositive skewNegative skewF I G U R E 2 .11Examples of differentshapes for distributions.48CHAPTER 2| Frequency Distributions
1.The seminar rooms in the library are identified by letters (A, B, C, and so on). Aprofessor records the number of classes held in each room during the fall semester.If these values are presented in a frequency distribution graph, what kind of graphwould be appropriate?

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Frequency distribution, researcher