Attribute data are usually collected when standard measurements are difficult to obtain. Continuous variables can have an infinite number of values, but attribute variables can only be classified into specified categories.
The advantage of continuous measurements is that they usually give much more information. The advantage of attribute data are that they are usually easier to collect. A disadvantage of attribute data is that they are usually subject to appraiser interpretation. For example, one appraiser may define a chip defect differently from other appraisers.