Stratified random sampling, Applied Statistics

Stratified Random Sampling:

This method of sampling is used when the population is comprised of natural subdivision of units, The method consist in classifying the population units into a certain numbers of groups called strata. Then random samples are selected   independently from each group. The division of the population into strata is done in such a way that.

(1)   There is greater homogeneity within each group also  called stratum;

(2)   There is no over lapping in various strata or groups.

In practice geographical, sociological and economic characteristics are used for dividing the universe into different strata.  For example, if is desired to study the wage levels of workers in an industry, it would be better to classify all works into skilled and unskilled males and females categories and then select random simple   from each group  in the ratio to the size of that group  in population. The size of sample from each strata may either be proportional or disproportional to  the size of each.

(a)    Proportional Size: Under this a given percentage of items are selected from each stratum. For example in case of 50% selection there will be a selection of 5 to 10 units and 10 of20 units. Consisting of 10 and 20 units. This selection will be at random following any of the methods discussed earlier.

(b)   Disproportional Size: A disproportional selection may also be followed if different strata reveal different levels of within strata variability. Following the normal sampling rules, a larger sample is recommended if some sub strata reveal greater degree of variability with regard to a phenomenon relevant to the inquiry in comparison to the general lot.

Posted Date: 9/26/2012 7:24:09 AM | Location : United States

Related Discussions:- Stratified random sampling, Assignment Help, Ask Question on Stratified random sampling, Get Answer, Expert's Help, Stratified random sampling Discussions

Write discussion on Stratified random sampling
Your posts are moderated
Related Questions
Mean Absolute Deviation To avoid the problem of positive and negative deviations canceling out each other, we can use the Mean Absolute Deviation which is given by

Ask 3. Precision Manufacturing has a government contract to produce stainless steel rods for use in military aircraft. Each rod is required to be 20 millimeters in diameter. Each

Make a decision about the given claim. Do not use any formal procedures and exact calculation. Use only the rare event rule. Claim: A coin favors head when tossed, and there

Types of cost-reimbursable contracts are:   Cost Plus Fixed Fee contract (CPPF): Compensation is based on a fixed sum independent of the final project cost. The customer a

Systematic Random Sampling This method  is generally used in such cases where a complete list of the population is available from which sample has to be selected. Under this

If the data set contains an odd number of items, the middle item of the array is the median. If there is an even number of items, the median is the average of the two items. If the

A manufacturer has received complaints that aging production equipment is forcing workers to work overtime in order to meet production quotas. Historically, the average hours worke

You are attempting to purchase a part from a specialty vendor. Your company requires a C p of at least 1.67 on a critical dimension of the part. The dimensional specific

Analysis of covariance (ANCOVA) It is initially used for an expansion of the analysis of variance which permits to the possible effects of continuous concomitant variables (suc