Statistical aspects of cell motility determinations with a modified chemotaxis assembly for multiwell filter assays

A multiple chamber assembly for determination of neutrophil migration consisting of disposable lower plastic chambers and an easily cleaned and inert upper chamber made of stainless steel was constructed and used in experimental work. Using results of chemotaxis determinations in the assembly and a statistical model the consequences of various ways to present cell migration data are discussed. With any method for multiple measurements of chemotaxis of cells from a given sample, there are occasional extreme results ('outliers') deviating considerably from other determinations. We show that the medians of chemotaxis determinations performed in triplicate are less influenced by such outliers than the mean values. The risk of an outlier affecting the median value was in our assembly about 0.2%, compared with a 10% chance of influencing the mean value.