Normal Distribution

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Normal Distribution
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Normal Distributions
A normal distribution is modeled by a bell-shaped
curve called a normal curve that is symmetric
around the mean.
Most of the data is around the middle of the curve
Median
MEAN
Mode
tails
tails

• Characteristics of a Normal Distribution
• Bell Shaped symmetric (left side is EXACT
  mirror of the right side)
• with the data more concentrated in the middle
  than in the tails
• Mean, Median, and Mode are the same value

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Examples of Normal Distribution Curves. They
all have the same characteristics of a normal
curve!
The difference is that there standard deviations
are NOT the same!
Standard deviation is a statistic that tells
you how tightly all of the values of your data
are clustered around the mean.
When the values are pretty tightly bunched
together the curve is steep and the standard
deviation is SMALL.
When the values are spread apart the bell curve
is relativity flat and the standard deviation is
LARGE.
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Empirical Rule!!!
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Empirical Rule!!!
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Empirical Rule!!!
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Finding a Normal Probability
mean
two standard deviations above the mean
Reminder Probability must be a number between 0
and 1
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Examples
A 0.84
A 0.16
A 0.34
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HOMEWORK

• P.266 (1-18 all)