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24 Cards in this Set
- Front
- Back
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What is a population? |
The whole set of items that are of interest. |
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What does a census do? |
Observes or measures every member of a population. |
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What does a sample do? |
Takes observations from a subset of the population which is used to find out information about the population as a whole. |
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What are the advantages of a census? |
Completely accurate. |
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What are the disadvantages of a census? |
Time consuming and expensive. Cannot be used during the testing process of an item as it destroys them. |
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What are the advantages of a sample? |
Less time consuming and expensive. Less data to process. |
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What are the disadvantages of a sample? |
Data may not be as accurate. Sample may not be large enough to give information about small sub-groups of the population. |
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What are the three methods of random sampling? |
Simple random sampling. Systematic sampling. Stratified sampling. |
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What is simple random sampling? |
A sample where every sample has an equal chance of being selected. |
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What is systematic sampling? |
A sample where the required elements are chosen at regular intervals from an ordered list. |
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What is stratified sampling? |
A sample where the population is divided into mutually exclusive strata and a random sample is taken from each. |
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How can you calculate the number of people we should sample from each stratum? |
Number in stratum/Number in population * overall sample size |
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What are the advantages of simple random sampling? |
Free of bias. Easy and cheap for small populations and small samples. Each sampling unit has a known and equal chance of selection. |
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What are the disadvantages of simple random sampling? |
Not suitable for large size. Sampling frame needed. |
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What are the advantages of systematic sampling? |
Simple and quick to use. Suitable for large samples and large populations. |
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What are the disadvantages of systematic sampling? |
Sampling frame is needed. Can introduce bias if the sampling frame isn’t random. |
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What are the advantages of stratified sampling? |
Sample reflects population structure. Proportional representation of groups within population. |
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What are the disadvantages of stratified sampling? |
Population classified into distinct strata. Sampling frame needed for each strata. Not suitable for large samples in each strata. |
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What is quota sampling? |
An interviewer or researched selects a sample that reflects the characteristics of the whole population. |
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What is opportunity sampling? |
Taking the sample from people who are available at the time the study is carried out and who fit the criteria you are looking for. |
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What are the advantages of quota sampling? |
Small sample can be representative of the population. No sampling frame. Quick, easy and inexpensive. |
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What are the disadvantages of opportunity sampling? |
Non-random sampling can be biased. Population must be divided into groups which can be expensive. Non-responses are not recorded as such. |
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What are the advantages of opportunity sampling? |
Easy to carry out. Inexpensive. |
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What are the disadvantages of opportunity sampling? |
Unlikely to provide a representative sample. Highly dependent on individual researcher. |
