009. Describing data sets. Organization and grouping. Introduction. Methods of Organizing Data

Almost every statistical effort begins with the process of collecting necessary data and thereby forming the data set to be used in the study. This collection of raw data in itself reveals very little. In order to determine data significance, we must organize them into some form so that, we can get an idea as what the data can tell us.

Statistical tools for organizing data include

· Frequency tables, which place all the data in specific classes.

· Various pictorial displays that can provide a handy visual representation of the data.

· Contingency tables and steam – and – leaf designs, which also allow presentation of a large data set in a concise, discernible form.

Methods of Organizing Data

Several basic tools can be used to describe and summarize a large data set. The simplest is an Ordered array.

Example 2.1 (if there’s a small data array). The IQ scores of five valedictorians from Podunk University are 75, 73, 91, 83 and 80. An ordered array merely lists these observations in ascending or descending order. The five values might thus appear as 73, 75, 80, 83, 91. The ordered array provides some organization to the data set; it can now readily be seen that the two extreme values are 73 and 91.

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