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High School Mathematics - 2
11.9 Normal and Skewed Distributions
Normal and skewed distributions:
The probability distributions we studied so far are
discrete probability distributions
because they have only a finite number of possible values.
A discrete probability distribution can be represented by a histogram.
continuous probability distribution
, the outcome can be any value in an interval of real numbers.
Continuous probability distributions are represented by curves instead of histograms.
Such curves are often called a
Many distributions with symmetric curves or histograms are
In normal distributions scores are more concentrated in the middle than in the tails.
A curve or histogram that is not symmetric represents a
Positive skew: The right tail is longer and the mass of the distribution is concentrated on the left of the figure. The distribution is said to be right-skewed.
Negative skew: The left tail is longer and the mass of the distribution is concentrated on the right of the figure. The distribution is said to be left-skewed.
: Determine whether the data 14, 15, 11, 13, 13, 14, 15, 14, 12, 13, 14, 15 appear to be positively skewed, negatively skewed, or normal distributed.
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