LECTURE 5 Frequency Distributions.pdf - LECTURE 5 Frequency Distributions S P 11 0 S TAT I S T I C S F O R P S Y C H O L O G Y OUTLINE Frequency

# LECTURE 5 Frequency Distributions.pdf - LECTURE 5 Frequency...

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LECTURE 5 Frequency Distributions SP110 STATISTICS FOR PSYCHOLOGY OUTLINE Frequency Distributions Shapes of Frequency Distributions Frequency Distributions A frequency distribution shows the pattern of frequencies over the various values. A frequency table or histogram describes a frequency distribution because each shows the pattern or shape of how the frequencies are spread out, or “distributed.” Describing the shape of a distribution is important, both in the descriptive statistics and also in the inferential statistics. Shapes of Frequency Distributions Unimodal, Bimodal, Multimodal and Rectangular Distributions Unimodal: Frequency distribution with one value clearly having a larger frequency than any other. (One peak, one value has clearly a larger frequency) Bimodal: distribution with two approximately equal frequencies, each clearly larger than any of the others. (Two peaks, two approximately equal frequencies) Multimodal: Frequency distribution with two or more high frequencies separated by a lower frequency. (Two more high frequencies) Rectangular: Frequency distribution in which all values have approximately the same frequency. (All values have about the same frequency) These figures are not histograms, but special line graphs called frequency polygons, which are another way to graph a frequency table. In a frequency polygon , the line moves from point to point. The height of each point shows the number of scores with that value. This creates a mountain-peak skyline Shapes of Frequency Distributions Unimodal, Bimodal, Multimodal and Rectangular Distributions Strictly speaking, a distribution is bimodal or multimodal only if the peaks are exactly equal. However, psychologists use these terms more informally to describe the general shape. The scores from most psychology studies are usually an approximately unimodal distribution. Bimodal and other multimodal distributions occasionally turn up. Shapes of Frequency Distributions Unimodal, Bimodal, Multimodal and Rectangular Distributions  