Stratified sampling is a method of sampling from a population in statistics. When sub-populations vary considerably, it is advantageous to sample each subpopulation (stratum) independently. Stratification is the process of grouping members of the population into relatively homogeneous subgroups before sampling.tratified sampling is a method of sampling from a population in statistics. When sub-populations vary considerably, it is advantageous to sample each subpopulation (stratum) independently. Stratification is the process of grouping members of the population into relatively homogeneous subgroups before sampling.
Hardening (computing) In computing, hardening is usually the process of securing a system by reducing its surface of vulnerability, which is larger when a system performs more functions; in principle a single-function system is more secure than a multipurpose one.
Flame-hardening is an ideal, time-tested method for steel hardening. And there are several types of steel that work well for the flame-hardening process. One example is hardening 4140 steel. Another is hardening 1045 steel. Flame-hardening cast iron has also been done with success. The clutch plate shown in the photo below is made of cast iron, as is the cam shaft sample shown to the right.