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Stats test notes:
Interquartile Range= third quartile minus first quartile
Sample variancesum of squared standard deviations divided by n1=(standard deviation)
squared
Coefficient of variation: ratio of standard deviation to the mean
Population variancedivide by N instead
Population standard deviation=square root of population variance
Skewed to the right=data is more to the left=positive skewness value
When the distribution is skewed right, the mean is usually greater than the
median.
When the distribution if skewed left, the median is usually grater than the mean.
Chebyshev’s theorem65 percent of data must be within 1.7 standard deviation of the
mean
Norman distributiondata clustered around the mean
Empirical rule65, 95, 99.7 percent of data are within 1,2,3 standard deviations of the
mean respectively.
Empirical rule may not hold for right skewed data
Lower limit=Q11.5(IQR)
Upper Limit=Q3+1.5(IQR)
Sample covariance=multiply deviations from the mean and divide by N1
Sample correlation coefficient=ratio of sample covariance to the product of the standard
deviations of both variables.
Weighted mean=multiply value by number of occurrences, add them all up, divide by
total number of occurrences
Sample mean for grouped data=sum of class midpoints times frequencies divided by total
frequencies.
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 Spring '09
 Smith

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