This article is part of a series on Medical statistics, edited by Jonathan Ball, Viv Bewick and Liz Cheek.

Review

Statistics review 1: Presenting and summarising data

Elise Whitley¹ and Jonathan Ball²

¹Lecturer in Medical Statistics, University of Bristol, Bristol, UK

²Lecturer in Intensive Care Medicine, St George's Hospital Medical School, London, UK

author email corresponding author email

Critical Care 2002, 6:66-71doi:10.1186/cc1455

Published:	29 November 2001

Abstract

The present review is the first in an ongoing guide to medical statistics, using specific examples from intensive care. The first step in any analysis is to describe and summarize the data. As well as becoming familiar with the data, this is also an opportunity to look for unusually high or low values (outliers), to check the assumptions required for statistical tests, and to decide the best way to categorize the data if this is necessary. In addition to tables and graphs, summary values are a convenient way to summarize large amounts of information. This review introduces some of these measures. It describes and gives examples of qualitative data (unordered and ordered) and quantitative data (discrete and continuous); how these types of data can be represented figuratively; the two important features of a quantitative dataset (location and variability); the measures of location (mean, median and mode); the measures of variability (range, interquartile range, standard deviation and variance); common distributions of clinical data; and simple transformations of positively skewed data.