Statistics Chapter 3b
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What are zscores often called?
Standardized scores

What can a zscore tell you?
How many standard deviations a value is from the mean

What is the zscore equation?
_{}

What is the mean of a zscore?
0

What is the standard deviation of a zscore?
1

What does the +/ mean terms of zscores?
 + 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 zscores 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