Selecting Optimal Statistical Tools

Extract

The first consideration in analyzing any data is to consider the architecture of study design and quality of the data. Numerous study designs exist, and they vary in their susceptibility to distorting biases. Maclure identifies 32 distinct combinations of taxonomic dimensions by ranking study designs on axes regarding (in decreasing order of importance) randomization, aggregation, parameter timing, selection/allocation, blinded-ness, and proximity. Maclure uses the term aggregation in favor of the often-used term ecologic because groupings may be based on nonspatial units (eg, occupation, family membership, birth periods, etc.), rather than places per se. Parameter timing refers to whether exposure or outcome is measured first or simultaneously; proximity refers to the relative time of measurements, ranging from historic to concurrent. His final figure, which summarizes a composition of six preliminary figures of taxonomic dimension, is reproduced here (Figure 1). Validity is strongest as one moves to the right of center in his summary figure. This taxonomy indicates that blinded randomized trials provide the strongest designs, nonrandomized aggregational studies suffer the greatest susceptibility to bias, and nonrandomized person-based studies rest between.