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Easy questions and answers on sampling techniques
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1 Sampling Methods
When surveying, for any purpose, it is important to recognise that the results are only as representative as the survey subjects (the sample), and as such much academic research has been performed in to techniques for selection, broadly placing them in one of two categories – probability sampling and non-probability sampling.
In short, with probability sampling the participants are selected by chance. There are dozens of methods of selecting members, using a variety of mathematical techniques, but the key is that each subject has a random, calculable chance of being selected. There is no human intervention involved in the selection.
Method Characteristics
Simple (random) Sampling The sample is selected entirely at random
Stratified The population is first divided in to exclusive subgroups based on some predetermined criteria (e.g. location), then samples are selected at random
Proportionate Stratified As above, but a smaller group that would otherwise not provide statistically valid results may be oversampled then the results weighted to correct for this. For example, if a particular group is too small to provide a statistically significant sample, more members of that group would be sampled
Clustering The starting point for the sample is randomised, then assumes that the sample at that point is representative of the region. For example, selecting a street corner, interviewing the first 10 people, and assuming that they are representative of the area
Table 2 - Probability Sampling Methods
Non-probability samples, however, contain an element of human bias in the sample selection. Again, there are various methods for the selection, the most common of which are:
Method Characteristics
Quota Respondents are preselected to ensure that the sample is representative
Purposive Subjects are selected as they have some specific characteristic, for example, hold a certain position or job type
Convenience The sample is selected by availability
Snowballing Contacts provide information about other potential respondents
Self-selection Respondents volunteer themselves for selection
Judgement An “expert” uses his or her judgement to nominate people for sample
Table 3 - Non-probability Sampling Methods
Most samples use a combination of sample selection methods. For example, quota sampling is often used to ensure that a random sample is actually representative of the population.
2 Survey types
There are three basic surveying techniques that are suitable for consideration in the project:
• Interview
• Telephone
• Self Administered Survey
2.1 Interview (face to face)
This category includes in-depth interviews, focus groups and projective methods (such as word association tests) which are not suitable for use in this project. There are several distinct advantages to this type of survey, such as:
• Response rates tend to be higher than other methods
• Ability to reassure the subject about their responses
This method is used since it is the most appropriate for calculating the mean and the standard deviation of a grouped data.
Not a random sample. They sampled “well-off people”. That subset of people may be the most likely to purchase, but they aren’t the only ones who can/would purchase their
The size of the sample must be quite small, because it is stated so in
We cannot sample the whole world as that would take an infinite amount of time. This is why we try to take a larger sample of the experiment for it to be more accurate.
Answer: The fact that an investigation of local restaurants was conducted in which 150 were selected randomly indicates that this is a sample. This sample indicates that out of the 150 randomly selected, 42% of this random selection out of the total population of restaurants possessed series health code violations.
...ristics such as age, race, gender, education etc. The only way to use this sample is if other methods are not available. In order for a purposive sampling approach to be successful, researchers need to be careful and not use results from previous convenience samples (Purposive sampling, 2012).
The research is not without its limitations. One of the challenges that would be faced would be establishing the accuracy and bias in the various answers given by respondents. Some of the information may be dishonest, biased and unclear. This would render the report unreliable.
Huff starts out by talking about the sample with a built-in bias. Data collected at the beginning of the study that is used to create statistics originates from someone or something. One of the problems with the data is someone may not answer the question honestly; therefore you do not get a truly unbiased response. The other way built in bias is noted occurs when the sample picker does not truly randomly select the people, or subjects and this introduces bias in the sample as well. One must be aware of how subjects are chosen and randomized.
After randomly choose the sample group. The 60 students will then be randomly assigned to 2 groups...
...sis, which could make all results invalid. With any research projects, limitations will be present. It is important to attempt to eliminate some of these causes in order to complete a thorough, accurate study. In future projects, this study could go about researching the issue in different ways. Perhaps using a larger sample size would be conducive for accurate results. A larger sample size helps reduce and even out any possible errors caused by those who do not answer truthfully. Also, keeping the surveys mainly anonymous would help to receive more truthful and accurate responses from participants. Participants may be fearful of judgments on open interviews or phone interviews, which could affect responses. In order to obtain as accurate results as possible, a future study would need to find ways to survey participants in a confidential way that feels comfortable.
-If the number of animals recaptured in the second sample (n2) is less than 8, the estimation of the population is likely to be biased.
Perhaps the greatest endeavor that owes itself to induction is science. Its claim to be in the pursuit of truth, of empirical knowledge, is entirely dependent on the validity of inductive reasoning. As such, science has developed ways and means to guarantee the validity of its conclusions; this includes randomizing samples, choosing appropriately sized sample groups and the use of statistics to calculate whether something is merely possible or is probable. Each of these methods (and there may be more) needs to be examined.
Maree (2007; 172) explains that when gathering data, making use of samples is an easy and convenient way to get general findings about the population you are using for your study because in reality it is usually impossible to include the entire population in your study as the most two restrictions being time and c...
Surveys are an effective and popular method for research because of the efficiency, versatility and generalizability. Generalizability is the ability to sample and draw research conclusions for large populations (Bachman & Schutt, 2012). In order to effectively maximize outcomes in survey research, surveys must be structured to avoid unclear or confusing questions. Demographic related questions should be avoided if not pertinent to the research study (Bachman & Schutt, 2012). Generally, the motivation of the researcher is clearly identified in a survey, and the respondent has the option of declining involvement in the survey. There are fewer ethical dilemmas with survey research than other types of research methods.
(i) How would you go about sampling 20 students from the class? Explain your answer (20%)