There are numerous ways to select a sample. You should choose the strongest possible method that is practical within your resources and the expertise of the evaluation team. Show
Random samples – as explained in the first table - are the strongest but they usually require the most resource and evaluation expertise. Non-random samples – as explained in the second table – are not as strong but may be more practical. How Many People Should Take Part?Ideally, get help from a statistician to determine the number of people to take part in your evaluation. If this is not possible then the following figures can be used as a rough guide. For questionnaires or surveys (mainly closed questions) try to have at least 50 people take part. If different groups are being compared you will need at 50 people per group e.g. 50 males and 50 females. In focus groups (mainly open questions) you should have somewhere between 4 and 12 people per focus group. You may do one or more focus groups. The total number of participants, over all groups, is less strict than questionnaires because focus groups are used to obtain rich detail rather than aim to be representative of the population (pupils in a school or year group, for example). Ways to Select a Sample
Which sampling method divides the population into groups?Cluster sampling divides the population into groups, then takes a random sample from each cluster. Both systematic sampling and cluster sampling are forms of random sampling, known as probability sampling, which stands in contrast to non-probability sampling.
In what type of sample would you divide the sample into groups?Stratified sampling
To use this sampling method, you divide the population into subgroups (called strata) based on the relevant characteristic (e.g. gender, age range, income bracket, job role). Based on the overall proportions of the population, you calculate how many people should be sampled from each subgroup.
What is the name of a sampling method when population is divided into groups then some random sample are selected from each groups?Cluster sampling divides the population into groups or clusters. A number of clusters are selected randomly to represent the total population, and then all units within selected clusters are included in the sample. No units from non-selected clusters are included in the sample.
What type of sampling is randomly selecting?Definition: Random sampling is a part of the sampling technique in which each sample has an equal probability of being chosen. A sample chosen randomly is meant to be an unbiased representation of the total population.
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