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Statistics Chapter 3b
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What are z-scores often called?
Standardized scores
What can a z-score tell you?
How many standard deviations a value is from the mean
What is the z-score equation?
_{}
What is the mean of a z-score?
0
What is the standard deviation of a z-score?
1
What does the +/- mean terms of z-scores?
+ value means how many standard deviations ABOVE the mean
- value means how many standard deviations BELOW the mean
What does the Empirical rule apply to?
Data that is "normally distributed"
Example
: skewness = 0, mean
median
What are the 3 parts to the Empirical rule?
68% of the values will be between z = -1 and z = +1
95% of the values will be between z = -2 and z = +2
99.7% of the values will be between z = -3 and z = +3
What are outliers?
Unusually small or large values in a dataset
What z-scores do outliers typically have?
z < -3 or z > +3
What could be the cause of an outlier?
Error
Evidence of something unusual
What does covariance measure?
Linear associate between 2 variables
What is the covariance equation for a sample statistic?
What is the covariance equation for a population parameter?
For a covariance, what does the sign tell you?
Positive = direct relationship
Negative = inverse relationship
For a covariance, what does the value tell you?
Nothing
What is the correlation coefficient equation for a sample statistic?
What is the correlation coefficient equation for a population parameter?
What does the correlation coefficient measure?
The strength of the relationship
How strong is the relationship for two variables with a correlation coefficient of .30?
Weak
How strong is the relationship for two variables with a correlation coefficient of .50?
Moderate
How strong is the relationship for two variables with a correlation coefficient of .80?
Strong
How strong is the relationship for two variables with a correlation coefficient of .90?
Very strong
Author
honestkyle
ID
198125
Card Set
Statistics Chapter 3b
Description
Standard deviation and variance calculations. Things are getting more difficult.
Updated
2013-04-11T16:17:03Z
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