There are various methods of quality control like 100 per cent check system, spot checking method and statistical quality control system. Under statistical quality control, observation for a fairly long period is made regarding the quality of the product. The observation enables to determine average quality of the product. The distribution of values is shown on a graph paper. A quality control chart is prepared which gives upper & lower limits of errors. The method of statistical quality control lower the cost of office •services and ensures greater accuracy. It lowers the cost of inspection and informs management when things are not going smoothly.