September 4, 2014

## Uni, bi, multi…

• Univariate data analysis - distribution of single variable

• Bivariate data analysis - relationship between two variables

• Multivariate data analysis - relationship between many variables at once, usually focusing on the relationship between two while conditioning for others

## Types of variables

• Numerical variables can be classified as continuous or discrete based on whether or not the variable can take on an infinite number of values or only non-negative whole numbers, respectively.

• If the variable is categorical, we can determine if it is ordinal based on whether or not the levels have a natural ordering.

## Describing shapes of numerical distributions

• shape:
• skewness: right-skewed, left-skewed, symmetric (skew is to the side of the longer tail)
• modality: unimodal, bimodal, multimodal, uniform
• center: mean (mean), median (median), mode (not always useful)
• spead: range (range), standard deviation (sd), inter-quartile range (IQR)
• unusal observations

## Now put these, and more, to use…

Complete application exercise 2 in teams, and submit on Sakai (one submission per team)