Statistics & Researche part4

Variance
?If measuring variance of population, denoted by ?2 (“sigma-squared”).
?If measuring variance of sample, denoted by s2 (“s-squared”).
?Measures average squared deviation of data points from their mean.
?Highly affected by outliers. Best for symmetric data.
?Problem is units are squared.
Choosing Appropriate Measure of Location
?If data are symmetric, the mean, median, and mode will be approximately the same.
?If data are multimodal, report the mean, median and/or mode for each subgroup.
?If data are skewed, report the median.
Coefficient of Variation (CV)
?Ratio of sample standard deviation to sample mean multiplied by 100.
?Measures relative variability, that is, variability relative to the magnitude of the data.
?Unitless, so good for comparing variation between two groups and for comparing variability of measurements in completely different scales and/or units.
%100??xsCV
Coefficient of Variation (CV)
?Ratio of sample standard deviation to sample mean multiplied by 100.
?Measures relative variability, that is, variability relative to the magnitude of the data.
?Unitless, so good for comparing variation between two groups and for comparing variability of measurements in completely different scales and/or units.
%100??xsCV