; This paper presents a method

called the standard-transformation and direct-plott ing method by the author

that utilizes the standard transformation of random variables to unify all kinds of control charts to a "universal control chart" with limits; UCL = 3

CL = 0

LCL=-3

and uses a direct plotting table or curves easily prepared before to relieve the workers from any calculation when they plot in the charts daily. Apparently

this method is very convenient in practice.In the cases that the size of the sample is not a fixed value

the limits of the current x

x

p and u control charts are concave-convex in shape

and therefore it is not only inconvenient to plot them but also difficult to judge if there are assignable causes. As to the pn control chart

because its central line is a function of n

we have to give it up in the n-var-ying situations. But the method proposed by this paper can avoid the drawbacks mentioned above

and increase the accuracy of alarm of the control charts

thus wide applications are ensured.