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.
Hard-Cemâ¢ is a concrete hardener developed for ready-mix and pre-cast concrete applications. Hard-Cemâ¢ is added to the concrete mix during the batching operation. Hard-Cemâ¢ is the only hardener of its kind that can be utilized in air-entrained concrete. Hard-Cemâ¢ overcomes the deficiencies of surface applied hardeners which are labor intensive, problematic for quality control and not suitable for air-entrained concrete applications.