Inferential Statistics [1] Descriptive statistics refers to statistical techniques used to summarise and describe a data set, and also to the statistics (measures) used in such summaries. Measures of central tendency, such as mean and median, and dispersion, such as range and standard deviation, are the main descriptive statistics. Displays of data, such as histograms and box-plots, are also considered techniques of descriptive statistics.
Inferential statistics, or statistical induction, means the use of statistics to make inferences concerning some unknown aspect of a population from a sample of that population. A common method used in inferential statistics is estimation. In estimation, the sample is used to estimate a parameter, and a confidence interval about the estimate is constructed. Other examples of inferential statistics methods include hypothesis testing, linear regression, and principle components analysis.
1. This definition is based in part on http://en.wikipedia.org/wiki/Inferential_statistics [disclaimer] and http://davidmlane.com/hyperstat/A29136.html.