Examples of Stratified Sampling in the following topics:

 As long as the starting point is randomized, systematic sampling is a type of probability sampling.
 Stratified sampling can increase the cost and complicate the research design.
 In quota sampling, the population is first segmented into mutually exclusive subgroups, just as in stratified sampling.
 In quota sampling the selection of the sample is nonrandom.
 Accidental sampling (or grab, convenience, or opportunity sampling) is a type of nonprobability sampling which involves the sample being drawn from that part of the population which is close to hand.
 Simple Random Sampling A simple random sampling (SRS) is a sample of a given size in which all such subsets of the frame are given an equal probability to be chosen.
 Systematic Sampling Systematic sampling relies on arranging the target population according to some ordering scheme, a random start, and then selecting elements at regular intervals through that ordered list.
 Stratified Sampling Stratified sampling is a method of probability sampling such that subpopulations within an overall population are identified and included in the sample selected in a balanced way.

 Identify some of the issues involved with creating questionnaires for surveys
Describe the various methods taken by pollsters to conduct surveys
Steps to conduct a poll effectively including identifying a sample, evaluating poll questions, and selecting a question and response mode.
 Identify and select potential sample members
Contact sampled individuals and collect data from those who are difficult to reach
Evaluate and test questions
Select the mode for posing questions and collecting responses
Train and supervise interviewers
Check data files for accuracy and internal consistency
Adjust survey estimates to correct for identified errors
Survey samples can be broadly divided into two types: probability samples and nonprobability samples.
 Stratified sampling is a method of probability sampling such that subpopulations within an overall population are identified and included in the sample.
 If the response option is yes/no then you will only know how many, or what percent, of your sample answered yes/no.
 Stratified Sampling Stratified sampling is a method of probability sampling such that subpopulations within an overall population are identified and included in the sample selected in a balanced way.

 The confidence level, the sample design for a survey, and in particular its sample size, determine the magnitude of the margin of error.
 It expresses the amount of random sampling error in a survey's results.
 The confidence level, the sample design for a survey, and in particular its sample size, determines the magnitude of the margin of error.
 If the exact confidence intervals are used the margin of error takes into account both sampling error and nonsampling error.
 Polls typically involve taking a sample from a certain population.
 Finite Population Correction The "finite population correction" (FPC) is used to adjust the margin of error to account for the added precision gained by sampling a larger percentage of the population.
 margin of error The margin of error is a statistic that expresses the amount of random sampling error in a survey's results.
 margin of error (noun) expression of the lack of precision in the results obtained from a sample

 Selfselection bias arises in any situation in which individuals select themselves into a group, causing a biased sample with nonprobability sampling.
 In practice, pollsters need to balance the cost of a large sample with the reduction in sampling error.
 Since some people do not answer calls from strangers or refuse to answer the poll, poll samples may not be representative samples from a population due to a nonresponse bias.
 Error due to bias does not become smaller with larger sample sizestaking a larger sample size simply repeats the same mistake on a larger scale.
 In statistics, selfselection bias arises in any situation in which individuals select themselves into a group, causing a biased sample with nonprobability sampling.
 Literary Digest The Literary Digest was an influential general interest weekly magazine published by Funk Wagnalls.
When the Digest conducted their 1936 election using an inaccurate sample causing them to predict the wrong winner, they lost all credibility and the Digest itself soon went out of business.

 Probability samples of internet polls are highly affected by problems of noncoverage.
 The difference between probability samples (where the inclusion probabilities for all units of the target population is known in advance) and nonprobability samples (which often require less time and effort but generally do not support statistical inference) is crucial.
 Probability samples are highly affected by problems of noncoverage (not all members of the general population have Internet access) and frame problems (online survey invitations are most conveniently distributed using email, but there are no email directories of the general population that might be used as a sampling frame).
 Due to the lack of sampling frames, many online survey invitations are published in the form of an URL link on web sites or in other media, which leads to sample selection bias that is out of research control and to nonprobability samples.
 Traditional solicitation modes, such as telephone or mail invitations to web surveys, can help overcoming probability sampling issues in online surveys.
 Telephone Polling Telephone polling is also fairly cost efficient, depending on local call charge structure, which makes it good for large national (or international) sampling frames.

 Discuss how public opinions surveys are designed and executed
An opinion poll is a survey of public opinion from a particular sample, and is designed to represent the opinions of a population.
 An opinion poll, sometimes simply referred to as a "poll," is a survey of public opinion from a particular sample .
 The most important aspects of a survey include:
Identifying and selecting potential sample members.
 Useful in describing the characteristics of a large population assuming the sampling is valid.
 Selfselection bias: Although the individuals chosen to participate in surveys are often randomly sampled, errors due to nonresponses may exist.
 SelfSelection Bias Although individuals chosen to participate in surveys are often randomly sampled, errors due to nonresponse may exist.
Some prospective respondents may simply be less likely to respond to polls generally, they may not be interested in the subject, or they may be unreachable for a variety of reasons.
 Opinion Poll (noun) An opinion poll, sometimes simply referred to as a "poll," is a survey of public opinion from a particular sample.
Opinion polls are usually designed to represent the opinions of a population by conducting a series of questions and then extrapolating generalities in ratio or within confidence intervals.

 One reason for their previous successes was the use of a very large sample population.
 In 1936, the Digest conducted their presidential poll with 2.3 million voters, a huge sample size.
 However, the sample turned out to be an inaccurate representation of the general population as those polled were generally more affluent Americans who tended to have Republican sympathies.
 At the same time, George Gallup conducted a far smaller, but more scientifically based survey, in which he polled a more demographically representative sample.
 " Researchers are also advised to replicate their polls, that is, "to see if identical analyses yield similar results for different samples of people
 Literary Digest The Literary Digest was an influential general interest weekly magazine published by Funk Wagnalls.
When the Digest conducted their 1936 election using an inaccurate sample causing them to predict the wrong winner, they lost all credibility and the Digest itself soon went out of business.

 Gallup was able to correctly predict the RooseveltLandon race by using a sample that was small, however, representative of the general population, while the Digest's mistake was using a large but skewed sample.
 In 1936, its 2.3 million "voters" constituted a huge sample; however, they were generally more affluent Americans who tended to have Republican sympathies.
 At the same time, George Gallup conducted a far smaller, but more scientifically based survey, in which he polled a demographically representative sample.
 Literary Digest The Literary Digest was an influential general interest weekly magazine published by Funk Wagnalls.
When the Digest conducted their 1936 election using an inaccurate sample causing them to predict the wrong winner, they lost all credibility and the Digest itself soon went out of business.

 There are nine main types of polls :
A polling place in New Jersey during the United States presidential election, 2008
An opinion poll is a survey of public opinion from a particular sample.
 In the deliberative opinion poll, a statistically representative sample of a community is gathered to discuss an issue in conditions that further deliberation.
 Citizens are invited by modern random sampling techniques to participate; a large enough sampling group will provide a relatively accurate representation of public opinion.

 Public opinion can be accurately obtained through a random sample survey, if done correctly.