Com 200 10/7/2010
Shapes and Distributions
We also previously discussed histograms
note that we could take a smooth curve along the top of a histogram to represent the
data
That curve is called a frequency curve
Shape Terms
Skewed
Skewed to the right: higher values more spread out than lower values
Skewed to the left: Lower values are more spread out than higher ones
Symmetric: if you were to draw a line through the center, picture on one side mirror
image of the other
Outliers: one or few scores far removed from the rest of the date
Unimodal: one prominent peak in a histogram or frequency curve
Bimodal: two prominent peaks
The normal curve
Normal curve: a distribution whose frequency curve is bell shaped
Many distributions follow this curve: pulse rate, IQ, male height, female height, overall
ideology of the population
If date from a population is normal, we can easily estimate the proportion of people
within any given interval on the curve
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 Fall '07
 Lillie
 Normal Distribution, Standard Deviation, #, 68%, curve Normal curve

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