This is called sampling. The group from which the data is drawn is a representative sample of the population the results of the study can be generalized to the population as a whole.
The sample will be representative of the population if the researcher uses a random selection procedure to choose participants. The group of units or individuals who have a legitimate chance of being selected are sometimes referred to as the sampling frame. If a researcher studied developmental milestones of preschool children and target licensed preschools to collect the data, the sampling frame would be all preschool aged children in those preschools. Students in those preschools could then be selected at random through a systematic method to participate in the study.
This does, however, lead to a discussion of biases in research. For example, low-income children may be less likely to be enrolled in preschool and therefore, may be excluded from the study. Extra care has to be taken to control biases when determining sampling techniques.
There are two main types of sampling: The difference between the two types is whether or not the sampling selection involves randomization. Randomization occurs when all members of the sampling frame have an equal opportunity of being selected for the study. Following is a discussion of probability and non-probability sampling and the different types of each.
Probability Sampling — Uses randomization and takes steps to ensure all members of a population have a chance of being selected. There are several variations on this type of sampling and following is a list of ways probability sampling may occur:. Non-probability Sampling — Does not rely on the use of randomization techniques to select members. This is typically done in studies where randomization is not possible in order to obtain a representative sample.
Bias is more of a concern with this type of sampling. The different types of non-probability sampling are as follows:. The following Slideshare presentation, Sampling in Quantitative and Qualitative Research — A practical how to, offers an overview of sampling methods for quantitative research and contrasts them with qualitative method for further understanding.
Examples of Data Collection Methods — Following is a link to a chart of data collection methods that examines types of data collection, advantages and challenges. Qualitative and Quantitative Data Collection Methods - The link below provides specific example of instruments and methods used to collect quantitative data. Sampling and Measurement - The link below defines sampling and discusses types of probability and nonprobability sampling.
Convenience sampling is easy to carry out, but one large disadvantage is that the sample is likely to be biased. Finally, quota sampling is another method of nonprobability sampling. This is when different subgroups are identified and participants are selected through convenience from each different subgroup.
For example, say a researcher wanted to select a sample of students to participate in a study using a convenience sample but wanted to ensure that an equal number of boys and girls were selected — quota sampling would be the best method for them to use.
This type of sampling can help to control a convenience sample but may results in a biased sample, which would not be a good representative of the wider population. As I mentioned earlier, the goal of research is to study a sample of participants and then generalise the results to the larger population. How far we can extend such results to generalise to a population is dependant on how closely the sample resembles the population — the representativeness.
The main threat to representativeness is bias. A biased sample is one which contains characteristics that are different from those of the population. This bias may happen by chance, but usually is down to selection bias. Selection bias is when participants are selected in a way that increases the probability of acquiring a biased sample. For example, if a researcher recruits participants from a gym, they are more likely to be healthier and fitter than the rest of the general public.
I can definitely say that the selection of participants is a very vital part of planning research. Without carefully planning and choosing an appropriate method for sampling it is very easy to obtain a biased sample that does not represent the population. When this happens, it is difficult to extend findings to a wider population and the validity of the experiment decreases. In order to produce influential and meaningful results, researchers must ensure that they have chosen an appropriate sampling method to select a representative sample of participants.
Behavioral study of obedience. Journal of Abnormal and Social Psychology, 72, This is a very interesting blog. I have written in one of my blogs about generalisation, and have never mentioned or considered sampling methods. Like you have mentioned convenience sampling is a cheap and easy way to recruit participants, and can lead to biases, which is something that I get really angry about, I know that it is impossible to be perfect on representing the entire population, but I just feel like some methods that are used shut off a large amount of people.
It is unlikely that research will ever represent the whole population, but it is good that there are a number of methods so that representation can be increased, and at the same time reduce biases. Homework for my TA. I have a question related to the sampling techniques described here. I will be grateful if you respond my queries please. Hi, suraiya khatoon, this was every intresting type of convenience sampling. The turn up was good hence less bias. I got what you intend, thankyou for putting up.
Woh I am lucky to find this website through google. Being intelligent is not a felony, but most societies evaluate it as at least a misdemeanor.
I want to know what is the basis? Hai I am Dr. Remya,I was searching sampling techniques as a part of my study,i found your blog useful,easily comprehensible. Reblogged this on innocenttauzen. Probability Sampling In probability sampling it is possible to both determine which sampling units belong to which sample and the probability that each sample will be selected.
The following sampling methods, which are listed in Chapter 4 , are types of probability sampling: Multistage Sampling in which some of the methods above are combined in stages Of the five methods listed above, students have the most trouble distinguishing between stratified sampling and cluster sampling.
Stratified Sampling is possible when it makes sense to partition the population into groups based on a factor that may influence the variable that is being measured. These groups are then called strata. An individual group is called a stratum. With stratified sampling one should: Under these conditions, stratification generally produces more precise estimates of the population percents than estimates that would be found from a simple random sample.
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Techniques > Research > Sampling > Choosing a sampling method Probability | Quota | Selective | Convenience | Ethnographic | See also There are many methods of sampling when doing research.
Sampling Methods. Sampling and types of sampling methods commonly used in quantitative research are discussed in the following module. Learning Objectives: Define sampling and randomization. Explain probability and non-probability sampling and describes the different types of each.
Feb 19, · So, in this weeks blog I am going to be discussing the different sampling techniques and methods, and considering the issue of sampling bias and the problems associated in research. There are a variety of different sampling methods available to researchers to select individuals for a . Simple Random Sampling (SRS) Stratified Sampling; Cluster Sampling; Systematic Sampling; Multistage Sampling (in which some of the methods above are combined in stages) Of the five methods listed above, students have the most trouble distinguishing between stratified sampling and cluster sampling.
RESEARCH METHOD - SAMPLING 1. Sampling Techniques & Samples Types 2. Outlines Sample definition Purpose of sampling Stages in the selection of a sample Types of sampling in quantitative researches Types of sampling in qualitative researches Ethical Considerations in Data Collection. This type of research is called a census study because data is gathered on every member of the population. Usually, the population is too large for the researcher to attempt to survey all of its members. A small, but carefully chosen sample can be used to represent the population. Sampling methods are classified as either probability or.