ABSTRACT
Describing data is an important step in the analysis process as well as in communicating results. Where the data are spread across a large number of values, each with low frequencies, it may be more effective to display the data by combining them into classes of equal sizes. The shape of the data when plotted on a frequency histogram is called the frequency distribution. When large samples of measurement data such as these are collected, the data often conform to a type of distribution called a normal distribution. Frequency histograms from sampled data can be compared to the ideal normal distribution. Data which are not symmetrical are said to be skewed. Distributions may also be skewed when the data are counts of items. The median is the middle data point when all the data points are listed in numerical order. The presentation methods used depend on the data and the reasons for display.
