1. A quality control system, comprising: user terminals each associated with at least one analyzer; and a quality control server connected to the analyzers and the user terminals via a network, wherein the quality control server comprises: a processor; and a memory operable under control of the processor and comprising a first database and a second database, the memory storing instructions enabling the processor to perform operations comprising: receiving from a first group of user terminals first sets of measurement information on a first category of control samples run by a first group of analyzers associated with the first group of user terminals, wherein the first category of control samples are correlated to the first group of analyzers; storing the first sets of measurement information in the first database, wherein the first database comprises identifications of the first category of control samples and measurement results obtained by running the first category of control sample at the first group of analyzers; receiving from a second group of user terminals second sets of measurement information on a second category of control samples run by a second group of analyzers associated with the second group of user terminals, wherein the second category of control samples are correlated to types of analyses performed by the second group of analyzers; storing the second sets of measurement information in the second database, wherein the second database comprises identifications of the second category of control samples, the types of analyses and identifications of the second group of analyzers, and wherein the first sets of measurement information are also storable in the second database; in response to a request from one user terminal, sending a selection screen for display on said one user terminal prompting a selection indicative of either the first control sample category or the second control sample category; in response to a selection indicative of the first control sample category, calculating first statistical data including a deviation of the measurement result obtained by an analyzer associated with said one user terminal among measurements results obtained by analyzers which run the same control sample in the first category; and in response to a selection indicative of the second category of control sample, calculating second statistical data including a deviation of the measurement result obtained by an analyzer of said one user terminal, the deviation being calculable among one group of measurement results selectable at said one user terminal from the following groups of measurement results: (a) measurement results by analyzers which run the same control sample in the second category; (b) measurement results by analyzers which run the same type of analysis, using the same control sample in the second category; and (c) measurement results by the same type of analyzers which run the same control sample in the second category.