Editing Descriptive statistics (section)

===Bivariate and multivariate analysis===

When a sample consists of more than one variable, descriptive statistics may be used to describe the relationship between pairs of variables. In this case, descriptive statistics include:

* [[Contingency table|Cross-tabulations]] and [[contingency tables]]
* Graphical representation via [[scatterplot]]s
* Quantitative measures of [[Correlation and dependence|dependence]]
* Descriptions of [[conditional distribution]]s

The main reason for differentiating univariate and bivariate analysis is that bivariate analysis is not only a simple descriptive analysis, but also it describes the relationship between two different variables.<ref>{{cite book |first=Earl R. |last=Babbie |title=The Practice of Social Research |url=https://archive.org/details/isbn_9780495598428 |url-access=registration |edition=12th |publisher=Wadsworth |year=2009 |isbn=978-0-495-59841-1 |pages=[https://archive.org/details/isbn_9780495598428/page/436 436–440] }}</ref> Quantitative measures of dependence include correlation (such as [[Pearson's r]] when both variables are continuous, or [[Spearman's rho]] if one or both are not) and [[covariance]] (which reflects the scale variables are measured on). The slope, in regression analysis, also reflects the relationship between variables. The unstandardised slope indicates the unit change in the criterion variable for a one unit change in the [[prediction|predictor]]. The standardised slope indicates this change in standardised ([[z-score]]) units. Highly skewed data are often transformed by taking logarithms. The use of logarithms makes graphs more symmetrical and look more similar to the [[normal distribution]], making them easier to interpret intuitively.<ref>{{cite book |first=Todd G. |last=Nick |chapter=Descriptive Statistics |title=Topics in Biostatistics |series=[[Methods in Molecular Biology]] |volume=404 |location=New York |publisher=Springer |year=2007 |pages=33–52 |isbn=978-1-58829-531-6 |doi=10.1007/978-1-59745-530-5_3 |pmid=18450044 }}</ref>{{rp|47}}