# Use of stratified random sampling; statistical control

1. When is it appropriate to use stratified random sampling.

2. What is meant when we say that a process is in statistical control?

3. Discuss ratio, interval, nominal and ordinal variables.

4. Explain what is meant by a margin of error for a confidence interval.

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Research Methods

Appropriate Use of Stratified Random Sampling

Stratified random sampling is basically concerned with the division of a population into smaller groups that is known as strata such as geographical areas, age groups, and genders and that is basically human and natural population. It is also concerned to groups of homogenous units of strata. Therefore, stratified random sampling is appropriate to use in several situation when the other sampling process are not appropriate to find out effective research result. Following are some reason to use stratified random sampling that is appropriate:

1. When a simple random sample is not properly balanced related to major grouping of the population, stratified random sampling is often used appropriately to find out the best result from collected data and at this stage it gives more precise information than simple random sampling for a given sample size (Scheaffer, Mendenhall, Ott & Gerow, 2011).

2. The stratified random sampling is appropriate at that situation when units of the population fall into non-overlapping groups (strata) and simple random samples are taken from each stratum. In this case a subset containing the characteristics of a larger population and samples are used in statistical testing when population sizes are too large for the test to include all possible members (Stern, 2004).

3. It is also appropriate in reducing the cost per observation in the survey and increase accuracy at given cost when other sampling method fails.

Statistical Control Process

It is quite common to provide the clarification of meaning of statistical control that is in process activity. According to McIntyre (2009), it means that the result is consistent to achieve and sufficient to provide the required data in the process. But, at the same time, it also explains that the achievable result is not necessarily satisfactory. Therefore, it ...

#### Solution Summary

The expert uses stratified random sampling and statistical controls. What is meant by a margin of error for a confidence intervals is determined.