Krippendorff's α (alpha) is a general statistical measure of agreement among observers, measuring devices, or coders of data, designed to indicate their reliability. As a general measure, it is applicable to data on various levels of measurement (metrics) and includes some known coefficients as special cases. As a statistical measure, it maps samples from a population of data into a single chance corrected coefficient, a scale, indicating the extent to which the population of data can be relied on or trusted in subsequent analyses. Alpha equates reliability with the reproducibility of the data-generating process, measured by the agreement on what the data in question refer to or mean. Typical applications of α are content analyses where volumes of text need to be read and categorized, ...