Looking back on your statistical tool

provided the original work is properly cited. CC In this issue, we bring attention to two specific articles. Each exhibit strong rhetoric, which is rare in the world of scientific journals, in which storytelling is generally considered to be trivial. In the first article, Park et al. [1] stated that some previously reported confidence intervals for 95% thresholds estimated with the up-and-down sequential (UDS) design were so large that they demonstrated a fixed-concentration design. While the text comprises a matter-of-fact description, those are also intriguing me to regard as their confession, in a sense. Park et al. is a leading group of authors of KJA articles in which the UDS design is described. One reviewer pointed out the weakness of the fixedconcentration (or fixed-dose) design (FCD) in that the FCD requires more subjects than does the UDS design. For our readers, I am summarizing a succinct aspect of the UDS design that has been described previously in other medical journals [2-4]. The dose (or concentration, even if omitted) of a median threshold is rapidly obtained with the UDS design, and its approximating speed depends on the estimation of the starting dose. The required sample size is smaller than that required for the FCD. Researchers are not compelled to calculate a minimum sample size when adopting the UDS design because it has a strict stopping rule. This is an advantage when studying a drug with unexplored properties. Conversely, each dose used in the UDS design relies on that used previously. This violates the assumptions of statistical tests that are based on generalized linear modeling (GLM), such as logistic regression and probit regression. The researcher must analyze the UDS data using only the UDS approach, not by GLM. The UDS design necessitates convergence of the data about a median threshold, and the data become sparser as they spread farther from the median. Any upper (90% or 95%) threshold calculated from the UDS data is then disputed, although readers often inquire about the upper threshold rather than the median threshold. Please refer to the following text taken from the report by Park et al. [1].